There are all kinds. I saw one guy but a foreclosure where the property was painted ugly grey and maroon and had tall weeds and full of trash. All they did was paint rotten wood and all and cut the grass and haul off the trash. I assume they actually closed on the deal and not just a wholesaler. If you just wholesale all you are doing is getting under contract and then reselling. Sure you may want to cut the grass and clean up trash to make it easier to sell. This may may have gone further and spent a few hundred of the paint job but I hope he got permission if he did not own it.
Finding buyers is easy. Local ad, local clubs, sign in yard, bandit signs, word of mouth. ads where they are looking for sellers. etc etc
I would imagine most are just folks and not small companies.