@Bilal
Exactly like said @Levin its going to cost more to maintain it, I do want to break your heart but hobbys do cost a lot to maintain, just like wives, lol! I am sure Levin will agree 
And just like @SER_GTR said go to Shershah and look around but with a good mechanic and better if you know the mechanic coz they can rip you off too, since the mechanics and the seller can have prior agreement. So I say find a good mechanic first, and then look for a good engine gtti engine. Definitly check for any missing parts and do ask a lot of question. I am not sure what kind of gurantee can u get on them but do ask for it. Coz unlike diesel engines you cannot start a petrol engine on the spot without the ECU and other electrical stuff. Yes they can just start the diesel engine sitting on the ground, check it out yourself. Well guys, can you add other things he should look for that I have not mention any cautions.