1. market value = transacted value (ever heard of the term "marked to market"?)

2. the way you describe value.. gave me an indication that you're a good "waterfish" target. you can only determine(with a degree of calculated risk) good value with a series of due-dilligence. have you done any besides the price factor alone?

3. having a proper appraised house is not your primary concern, but having an approval of the loan amount is. have you heard of the term "pre-approve loan"? the process of having it pre-approved acts also as a sanity check... if you're suitable to swallow such debt and if the valuation of the said property is sound.

4. walking away from a deal with an agreement and not to buy is not free-lunch, it's not binding unless you're foolish enough to sign some legally binding papers without exit clause!! what you'll loose is the 2%.

...treat that as a learning fee if you have to walk away (for that's one good education you'll get, albeit the pricey fee)