My experience has been that people starting out in the industry often must charge far less. I, for example, have had to charge several people $5 to $7.50 a page just to get them interested since they were so poor. I write well, am not an ESL writer and am nationally published, but I personally have a base rate of $7.50, though I do get up to around $17.50.
To get a feel for the reputability of a site, I always go for the obvious: Do THEY write well? Many sites have nice, professional looking backgrounds, but the moment you read a section that isn't the front page or get an e-mail from them, it is full of broken English, misspellings, grammatical errors, etc. Further, if their writing just seems hackneyed or uninteresting, how can they write a good paper for you?
Of course, if you're paying $25-35, there is a very good chance they are hiring master's and Ph. D students. That is a good thing for you, obviously.