Is there a time window or are there other limitations for getting a writ of abandonment?

Define your limits... if this happens then I should do this type of thing. 

He is totally retired living on the Florida intercoastal waterway with all the toys and lifestyle you can imagine. 

It may not be if you've got regular W-2 income that brings you close to the social security limit or if you want to contribute the maximum amount to a SEP.  

I have limited MLS access and I haven't seen it as a property for sale.  

Based on what you said it's worth, you're well within the limits. 

We do have a 0% down mortgage program for first time resident buyers (that can only be used once), but the property purchase limit is $200,000 and it is difficult to find multi-unit properties in this price range - unless they are in a C or even D area.

If you're in Houston you should look up Lifestyles Quest or Investway.  

That said, with the limited information you've given, there is still probably some meat on the bone.I can't do accurate math for you because a lot of it is very case by case, but major expenditures you should add in are vacancy, roof, HVAC, property management, and any concessions you give tenants such as free water, cable, yard maintenance, etc.

Sadly, limited information exists for folks heavy in RE investments.