Hi Marquell, in Alabama the right of redemption is 3 years and the tax sale in my county is once a year in May (this may be true in all Alabama counties). So if you buy one next May for $2k, the former owner could come up with the $2k plus interest and redeem it so your profit would only be the interest. During the redemption period you can't sell it and of course you wouldn't want to put any money into the property. I'm not sure if you can rent it or not but if so the renters would have to agree to vacate at any time in case the property was redeemed.
A state representative told me a while back they're trying to get the redemption period changed from 3 years to 6 months in AL but I haven't seen where that has happened yet.
Bottom line - if you can afford to bid and win a property and sit and wait for three years it can be a good deal.
I don't know the answer to your mortgage question but I'm curious to see the answer.