When I get a house under contract to wholesale or buy it with OPM, Do I have to show the seller my income or credit history? or Can I just go and get the house under contract?

Depends on what the seller wants.

There are no "hard & fast" rules.  Be aware that very, very few people in this world will hand you a valuable asset or cash unless you have something of value to exchange for it.  

@Account Closed, no, but you may be asked to provide either proof of funds or a lender's pre-approval.

@Jaysen Medhurst so if I tell them that a cash buyer will buy it then its ok

@Fili Aguirre, I don’t wholesale, so am not the best source. Have you searched the wholesaling forum?

@Jaysen Medhurst yea, I did. Thanks