Some of which have been noted.
Most SBs are part-time. Usually they have a day job but still come up short financially due to credit card expenses, college loans, etc. A few are career SBs or pros/semi-pros.
Some do it because they love/need sex and might as well make some money while having fun. There are some very horny, nearly insatiable women out there.
Chemistry is important. SBs screen for that, whereas pros screen for security.
Though I was just quoted a per-hour rate yesterday, generally SB dates are priced per date rather than per hour. Roughly, 1 hour with a pro costs the same as 3 hours with a SB, which explains much of the appeal. Some SBs think 45 minutes is adequate, but most are fine with 2-3 hours. Generally speaking overnights with a SB cost the same as a 3-hour date or, at most, 20-40% more. In the pro world, an overnight costs 400-800% of the hourly rate.
SB arrangements tend to involve more socialization and connection than pro date. There is often more repeating than in the pro world.
Though many SBs want to be exclusive, relatively few actually find that.
Many SBs have an odd mindset. They don't view it as P4P. They need to find a guy they would have sex with (based on chemistry) and they view the cash as separate.
A few SBs don't want sex. They want money for companionship or because they are pretty. Only a few guys are interested in that. Some women who happen to be beautiful and know it, expect guys to pay them just for their looks. That attitude is a huge turnoff.
SBs and pros, interestingly, look down on each other.
For your situation, I would not recommend the SB scene generally speaking. Once you have built your website and your reputation/brand, you have done the hard work and being a pro is more lucrative. However, here are possible SB benefits to you: you may find the whale willing to pay you lots of money for being exclusive; there is much less of a LE risk (pretty much none); you don't have any overhead costs or need to pay for hotels; if business is slow, you can fill the gaps with a SD; if you particularly like a client or a few of them, being a SB with them will encourage more and longer dates; there is less social stigma from being a SB than a pro.