Back Bay, Cambridge - Not as expensive as say middle of Boston, but with all the graduation going around, hotels are very expensive and hard to find these days.

You should look for good suburbs right outside of Boston. They are usually easily accessible to those living inside and outside of the city. Search for typical Boston suburbs that offer good prices on hotels.

If you prefer the city, they I'd recommend the Back Bay.  The downside is that visitors will need to pay for parking (unless they're in the neighborhood).  It's nice and safe and there's a good amount to do.

In the suburbs, I personally prefer Waltham.  The downside is that there's nothing for the ladies to do when they're not working.

I look for ads on TER, CityVibe and Backpage.  Most people on this site recommend strongly against back page, but I like it because it let's you know that the ladies are available (there's a lot of crap there, but even wonderful providers like Ally Moore and Ava use it).  I generally don't like Eros, but that's just me.

Back Bay and Cambridge are convenient and accessible and it is easy to blend in at the larger hotels.  Hotels in the Boston area are scarce and pricey at this time of year because of graduations and conventions, and so the Route 95 belt west of the city, where hotel rooms are a bit less expensive, is also a popular choice.

In terms of boards, I mostly look at TER and Eros.  On Eros, like most ad boards, there are scammers and ripoff artists mixed in with the genuine ads.

Good luck.  We'll look forward to the arrival of your beautiful ladies.

DJ