I had them confirm the last tenant didn't shut the vent and they confirmed cold air in their opinion was blowing out the vent. 

Shall I choose a hot, neutral, or cold market for wholesaling?

Sheesh, must be the cold medicine.

This includes knocking on doors, cold calling or driving for dollars (this one is my favorite).

On top of that, networking with other agents helps, as you can refer prospects to one another.Another thing that you can do is cold call.

In Bridgeport Connecticut where it snows and gets bitter cold we have to explain why we need to tune up furnaces BEFORE the winter hits to prevent problems like no heat or frozen pipes. 

If the deal is good enough, i would inherit the tenants and get rid of them one at a time. especially in this cold winter. let them pay the heating bill for another month..lol

Plus I need to learn how to cold call before I can expect someone to cold call for me successfully.

If someone rents out the place because they want to rebuild an engine and it's better to do that in your warm living room than their cold garage, guess who gets stuck with the cleanup (Yes I know a guy who had a short term rental used for that very purpose).

Do your research and as others mentioned you may want to find a wholesaler you can get you a great under market deal or find a target seller demographic and mail or cold call until you strike gold my friend.