I think you're confusing "beta" with "editor".
It sounds like what you're looking for is someone to read your work and give you opinions and try to catch that nit-picky stuff before you start submitting it. I know you said you don't want to just email stuff to someone online, but truth be told, I would trust the people on this board FAR before I'd trust some random schmoe from Craigslist. Craigslist is good for a lot of things, I have gotten jobs, and apartments, and sold a car on there, but I would fear anyone who answers an ad for an editor would be out to swindle you somehow. Whereas here, on this board, or online in general in specific social groups, you can read people's posts for themselves and come to your own conclusion on if they would be a good beta reader. My main beta is a woman I've never met IRL who lives in the west coast, but used to be a member, and then a moderator, on a message board I run. She says she went to an Ivy League college; is it true? I believe her. Could she be lying? Yeah, but her knowledge of SF&F is strong and she's a good beta. My (likely) secondary beta is another woman I've never met in person from Alaska who I met and friended via Livejournal on the sfandfwriters LJ community. I would trust either of them, literally sight unseen, before I'd trust some wannabe from Craigslist who's probably out for money, because I've spent literally years interacting with them online, and reading their own thoughts on writing and the SF&F genre. They know their stuff at least as well as I do, and compliment me just fine.
Once you sell your work to a publishing house, as far as I understand it, an actual in-house professional editor will go over your work again, making suggestions and the like. They're the ones that are the pros, and you won't find them on Craigslist, you'll come across them via your agent, or via the publishing house itself. I don't believe you get to really "choose" them; it's a working relationship you'll have, although hopefully it will be a good working relationship. Once you get to this point, you won't need to throw away your test readers/betas that you personally chose yourself, you're free to still run things through them, but the publishing house editor is the one that will work with you on your story for the final publication. They have the power of Yea and Nay.
(at least this is how I understand the process; full disclosure, I've not sold a novel yet. Those of you who have, correct me if I'm wrong.)