I provide huge value to them by delivering a product for their clients, and they provide huge value to me since I get more eyes into the property that I'm selling and am favored from an already built-in relationship and trust between the agent and buyer.

Can you spend the 10k on landscaping and sell the house for 50k more? 

Why not sell at a stepped up basis and pay zero taxes Uncle Sam?

If you are ever forced to sell you are very likely screwed.

He's tired of keeping up with his rentals and selling them off to his kids. 

Windows are also a nice value-add to the property once it comes time to sell. - Troy 

The tax implications in the future will be this: less depreciation after year one (not by much as transient property is depreciated over 39 years not 27.5) and if you ever sell the property you will have significantly more depreciation to recapture. 

The cons are that wholesaling is in almost every circumstance, unlicensed selling of real estate and illegal in most cases. 

You season it for around 90 days and you as the owner sell the property.

Deals that are sold quickly usually leave less information, and deals that take more time to sell usually leave more.