What is the safest way to buy a website, let's say the website cost about $5K (domain+content). It's a lot of money and people are ready to rip you off. How can you make this deal safe? Ok, first you determine that the seller is really the owner of the domain, what's next?
For that kind of money I would only do the deal using an escrow service. Even if I had to pay the full fee myself.
that or either meet face to face with the person selling the site. if you can afford 5k to buy a website you can afford some traveling.
For this,you need a middle man to prevent scam. I advise you to pay for escrow service. You need to verify the seller claim earning by putting your own ads into the website. Then check for the PR of the site.
There's a lot more due diligence to be done after that. There isn't much around on the net with respect due diligence on website purchases but perhaps this link would help. It covers doing some research on the seller and the site, how to diagnose fake traffic etc.
Escrow is the appropriate way for transferring domains. Escrow has an exlcusive process for domain transfer deals.