hello, I am a wholesaler. If I get a seller under contract and they have tenants in the property do I need to get them out before I assign the contract to an investor or does the investor do that?

You can't legally make them move with a tenant contract. I usually try to get them on my side by being nice and offering money. It's easier to deal with these situations in a sub2 because you have more time to work. It really depends on if it's a good tenant or not and eviction depends on your state but is never quick imo.