They could even negotiate a loan modification that might allow for the borrower that was once performing get back to reperforming. 

Ask them what the terms are for the modification & determine if that will work for your situation & it is affordable compared to your other options. 

It's a clue and reason to be on your list of targets.However, as David mentions, most are paid (late) without necessitating a sale.Now, if you combine your tax list with other triggers such as foreclosure and probate, etc. you can build some pretty incredible motivated Sellers.

The house I live in, I was able to get a modification.

If there's any modification that can get immediate profits, do it. 

You will need to take it down if your lease says something like modifications are not permitted without first receiving permission from the landlord.You may have done a great job, but the porch used to be open air and it is now mostly opaque.  

However, I'm trying to decide if I want to go a step further and go ahead with some the modifications I think need made to sell at full retail.

I have no idea what the laws are there but before you make any significant modifications, you may want to look into this, it could hurt you at resale time if you go about this un-permitted. 2) I'd also double check with the HOA that you've interpreted the bylaws correctly before you start.

I could buy properly zoned land, make any needed modifications required by state or local area, and only purchase a small amount of containers.

They bought the house 2 years ago and have already done a loan modification.