You've gotten a variety of advice here, some of which I agree with and other parts I do not. I do think that it's too soon for you to start talking with an agent/realtor, since you are still trying to figure out how much you can borrow now, if you can borrow, or whether you would want to borrow at all - if the rate is high. So ... first things first - is figure out what the scoop is on the "lending front".
It sounds like you may have already spoken with either a direct lender or a mortgage broker already. So, if they have "run your credit" in the last 2 weeks, it still counts as the same query if someone else does it again for the "same purpose" (mortgage - NOT "credit card" or "car loan", etc). It has generally been my personal experience that I've gotten the best rates from Wells Fargo. BUT ... I don't know if they deal with sub-prime mortgages these days.
Usually, with a low credit score, lenders charge substantially more for lending you money. So instead of getting say 5% or so, you might pay 6.5 or even more! Over time this would cost you a lot of money. Some people seem to feel that FHA loans are at the same rate, regardless of credit score. I'm not personally sure on that account but I would be surprised.
My recommendation is, sure - talk with a lender and know what your options are right now - IF you proceed forward. Assuming that I'm correct, and that they'll quote you a high interest rate for that loan (if you offer you one), then I would think that you may wish to reconsider how you approach it short-term - and just spend 3-6 months building up your credit. You certainly do NOT need to engage the services of any company to help with this - most ways of improving your credit are very manageable to handle on your own. I'm not a fan of most of the companies that would "help" with your credit. Most of them just want your money.
You are already familiar with Earned Income Tax, but it varies by municipality, so this might factor into where you look into buying, now or later. Here's the official link on EIT rates for PA: http://munstatspa.dced.state.pa.us/Registers.aspx
Pat - I hope that this has been helpful for you, and please do feel free to respond with more information or ask more questions!