By that, I mean if I qualify for say a max of $300k for a house, is that the same max for a multi as well?

How should I evaluate a "deal" in which the original owner has say a $20,000 loan?

You may not like what I have to say as it's not what you expect.  

Say a standard bank rate at the time.

That is significantly shorter then say a negligent misrepresentation claim.I get these types of call on at least a weekly basis. 

Also, more alarming, you say a better property is on the market for $225k and you're looking at paying $575k....???

If you're self employed, your tax returns might be a little more complex than say a traditional wage earner.

The box they leave in the basement is *always* going to say a number greater than 4.0, because that's what the testing company - which is also the remediation company - needs it to say to sell the work.I'd really love to call for a radon test on a house, let them put the box in the basement, and then move it out into the fresh air and sunshine in the back yard after they leave. 

If they say a number that is close to your initial ballpark of an acceptable purchase price, the lead is still alive.

I am fairly interested in what others have to say as well and would like to offer my two cents to start off the conversation.