Absolutely any market on this planet... so long as you get the property under contract at the right price point(discount) 

The best market IMO is your backyard. Working local is a great way to get comfortable with the wholesaling process. Especially when it comes to determining value!

Unless you live in ghost town, I would suggest sticking it out locally. 

If you absolutely had to, OH, FL, TN, MO, KY, GA, TX all have really good markets.