I worked for studio20 when I first started camming, my experience there wasnt great, the "trainers / admin" they had working actually ended up loosing me money, there was a bunch of other issues I had with them too which got me to leave after only 2 months there (mainly not holding up their end of what was agreed when I signed with them.) This was studio20 in Romania, your experience may be different, but when I went and spoke to them before signing I got them to be very specific in what the terms of the deal were (because of the language barrier and the fact my contract was in a language I cant read, I felt it was important to have them clearly explain all the details).
Depending on what you are expecting to earn you might be better off renting a 2nd place to cam from, here in Romania the standard rate for a studio is 50% of your earnings and you are stuck working on the sites that they put you on, you also give up all access to any other income such as clips and fan club sites because you sign over the rights to your image to them, meaning creating your own content to sell outside of the studio would put you in a breech of contract.
Some things you might want to ask them are:
The % they take from your earnings.
Any fee's and fines that may come up (they tried to fine me $100 out of the $120 I was earning saying one of the sites emailed them with screenshots that I broke some of the sites rules....they decided to drop the fine when I insited that they forward me the email).
Schedule you need to keep.
The sites that you will be working on. A lot of male studios here like to put guys on flirt4free...working for a studio I would say it's not worth it as you will be making about 1.25 cents per credit if they take a 50% fee (flirt4free credits are valued at 2.5cents each)