Well, I was relatively naive but luckily the person was honest. So I did not have issues. But here are some suggestions. 1) Open an escrow account, pay some money for it. 2) Put source code, domain name transfership, any business doducments in that escrow. 3) Ask seller to provider support to you for 1-3 months. This should go into contract. 4) Release money in installmeents. 5) Release from escrow only after you are satisfied!