General guidelines in terms of legitimacy of a writing service to write for?

Hi everyone,

Jumping into this thread to try and get some opinions. I'm a freelance writer, (10 plus years). I've done a lot of essay writing for clients in the past, but only through private means; never with a 'company'. However, one of my critique buddies started writing with a company a few months ago, not sure of the name, I just know that she seems to enjoy it. When I'm looking at the different companies out there, are there any general guidelines to keep in mind in terms of legitimacy? I don't want to not get paid! (I'm sure we've all had clients that skipped town, it's always a pain in the you know what). One thing I'm worried about is that even though my crit partner gave specific parameters for what she wanted to write, she consistently gets topics that don't match those. I'm not going to make any pretenses about being an expert in biology etc! If I say I only want to cover English Lit topics, will they honor that? Thanks for any info! :)

Bella