I would have thought there'd be some kind of rule preventing that.

Obviously, as I am not an attorney, please ensure if there is a certain state specific regulation that would prevent such a transaction.Stephen

Is it still possible for me to make him a cash offer and prevent foreclosure and sheriff sale?

I showed @David Krulacvia PM  a property that underwent what I will nickname "the trifecta" - it had been sold by the TCB, then the mortgage foreclosed (on the buyer at TCB), then the school district had the property sold at sheriff sale to cover unpaid school taxes (the lender's lien was no longer in effect because of the mortgage foreclosure sheriff sale, and lender did not cover the school taxes to prevent that sale).

There are also signs of a cover up at the base of the foundation because there are new concrete blocks there to hide the foundation and a temporary drain placed nearby to prevent water from reaching the foundation.

Household dehumidifiers will likely be insufficient for this -- you'll need commercial grade equipment.To prevent a repeat problem in the future:  I live here in Baltimore and based on what I saw yesterday, I don't think a sump pump will prevent this from happening again. 

It might prevent drafts in very old windows but there are better and less expensive methods. 

This is to prevent people from being cute and playing this short, 15+% return game.

Lots of factors at play that would prevent an investor, especially a new one like the O.P. from accomplishing this task.Market is hot right now.

What prevents you willing do personal guarantee if you believe the deal is so good?