Brent,
There's an RV-4 specific section here and you can use the search feature to dig out some info. The big things to watch out for are:
1. Cracked engine mounts/firewall damage
2. Sloshed fuel tanks (early airplanes).
3. Cracked control surfaces.
I'll suggest that you start by finding a local A&P who will work with you. As a buyer, you will need an A&P signoff at "annual" time. Many A&Ps are leery of working on homebuilts. All of them will have some personal opinions that you may not agree with. When you're asking a guy to sign his name in your logbook, you'lre going to have to do things his way (or find somebody else).
Next, you need to decide what kind of airplane you want/need. Are you looking for a 200HP firebreather or are you looking for a simple airplane that will be low maintenance ?
I assume you've had the opportunity to fly RVs already, so we'll skip that suggestion.
Then it's off to TAP, Barnstormers, etc. and be PATIENT.
Lastly, I'll make another oddball suggestion
![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
. Try to agree on a price BEFORE you go to look at a plane. When you find a plane you like, call the seller and basically say that if the plane is as represented, it's worth $50k (for example) to me. I won't try to negotiate further based on the inpsection. If it's not up to snuff, I'll walk. Otherwise, the buyer knows he's going to get $50k and may be more willing to meet your price. This can save a lot of time, travel, expense and aggravation over a deal that's just not gonna happen.
Anyway, let us know if we can help and good luck.
John