I did not know that applying wax to Brazilian Mail was some violation of the postal code. In any event, if that is a problem in your local, then you knew from the start you were applying wax to roman candles. That said, the question is what do you do now?

You should have nothing to fear from your present landlord-ass as she wants the moo-laa so she can dance the hula. Why she would interject  herself after the sale is questionable.  Is her hubby Brazilian? If she permitted your business then one could argue that she is complicit in the on goings, although most courts have too many landlords in their ranks to go after her. If she is a real threat in your opinion you might speak to her or have an attorney contact her to point out her complicity as well as the legal consequences of interfering with contract etc. and suggest that you intend to list her as a partner should the local waxing crew break in. At the same time you might want to lock your doors and refuse clients who you have not serviced before until the current threat goes away.

I don’t know the exact nature of your activities but you might also want to discuss those with me (pm) or someone else to make sure that the penalties are not excessive. Also, if you are using the local for activities that are not stipulated in the lease, depending on your contract terms, there is the possibility the lease can be rescinded. In such a case you would not be liable for the time lesft on the lease. In this day of difficult income, I would expect the new landlord would be happy to let you continue, however you might want to meet him and get a take on his view of waxing, saying your are considering moving to larger quarters and want to be sure if you stay that your business will not be disrupted due to rumors on innuendo that applies to the waxing and waning of economic affairs.

On the other hand, if you are offering any illegal services (i.e. sex for pay) then you should worry as it sound like your soon to be former landlord is planning to drop a dime on you.

This means that it is very possible LE will send in a decoy, ask for some sexual service and bust you if such service is offered for a fee.

Hence, you better lay low for a while on these services with anyone other than trusted clients until some months have passed.

You can consult a lawyer, but I don't know exactly how that's going to prevent problems.  The lawyer may have some further suggestions on what you can do to be proactive.

still not a lawyer

My main practice area at this time is commercial leasing. The main clauses in your lease that should concern you are your permitted use clause and the assignment clause. Your permitted use clause should state exactly what the premises can (and can't) be used for. It may be very specific (i.e., waxing services) or it may have some general language like "any lawful purpose". Just make sure you're using the premises only for the uses permitted in the lease. If it says any lawful purpose, you can obviously use it for anything that doesn't break the law. If your business is totally on the up and up and it is a permitted use, you should be fine. If you are using the premises for something not permitted under the lease (or less than completely legal), you could be served with a default notice telling you to abide by the lease, a court order which orders you to stop your business practices (or just those that violate the lease), or lastly a notice to quit (eviction) for breaking a material provision of the lease.

Let's assume that you have no problem with the permitted use clause. What does your lease say about the landlord assigning the lease to a new landlord?  Hopefully it should state that the new landlord must recognize the lease as it is written and cannot change anything as long as you are not in violation or default of any other lease provision. This is called a non-disturbance agreement. If your lease does not contain any language such as this, you might want to talk with a local attorney to see if you can have him or her draft a simple one. The trick is getting the new landlord to sign it. They may not want to and you don't have much leverage to negotiate with them. This may be an indication that they aren't too pleased to have you as a tenant. At that point you should definately talk to an attorney about a reasonable exit strategy. If they agree to sign it, you are all set from a landlord/tenant perspective.

As for your old landlord dropping a dime on you, all I can suggest is to be careful with your clients. If your services are completely legal, you should not be in any danger. You may see increased patrols, they may ask your patrons some questions, all of this may result in a temporary drop in customers. Eventually the heat will get board and move onto more productive pursuits.

I was a paretner in a campground, partner wanted to retire & I couldn't prevent a sale.  (Bad planning on my part.)  Transaction took place on 1 Jan after deposits recieved for the following year.  A lot of customers had worked their way up the list to get choice spots.   The deposits & reservations were transfered to the new owner.   The next installment was due mid-winter.  It was not unusual for a customer to not pay on the exact date but to stop in on the weekend to check their tarps & pay the next installment.  
The new owner cancelled all reservations which did not make the due date...  and raised the rates by 50%.  When customers wanted to reinstate their reservation it was at the new rate.   Myself & partner were no longer involved & powerless to interviene.  The objective was to increase revenue and free space for units for the franchaise they brought in.  It broke my heart to have good customers of many years treated this way but it was within the contract.  
skb

There's a little more to my situation, but hoping my current bitter landlady will have too much on her plate after the sale to bother remembering me. Thanks for all the feedback.
I did have my lease reviewed by an attorney before signing. My lease states "SPA Services" for my business.

Go to pains to make your spa look like a spa.  All necessary supplies for ALL services listed.  

One FBSM provider I see sometimes has a mini-spa set up her spare room.  Full comercial fire alarm & exit signs, crash bars.  The spa features an aquarium, scents, soft lighting, music, choice of warm oils...  her door is not supposed to be locked during business hours and no door on the spa room is allowed.  But her door gets locked...  no one will ever find out because the common entrance hall is kept locked & one must phone for admitance.  (She is dressed when she comes down to let you in...  it's a common hall remember.)  She rents an extra parking space reserved & marked for her business.  

Another FBSM (+) lady I see has a legit home business.  Her neighbors all think ALL her traffic is for the business.  She also has a second space for her clients.

Is to not take new clients for awhile and start having a few lady friends drop by for a visit each week as if they're customers.

for municipal code violations only.  Maybe a LMT lic not required or they had one.  But they nailed them for all the code violations.  They don't even need to "bust" you doing something we'd think of as illegal...  just inspect the premises.

but once it's done, it's done.  And it's an easy bust if the location has these codes.  (No need to prove illegal acts.)  As a business stratigy,  I'd work with the new owner to make sure you are up to codes...  no point in making it easy for someone to mess with you.  
My state passed the toughest Fire Codes in the US following a horrific nightclub fire.  A guy near me runs a mower shop out of a detached garage...  only open with the door up!  Had to put in fire alarm though.