Supportive Housing Grants, Housing Choice Vouchers,  Shared & Sheltered housing program, Home Modification Grant, HUD Vouchers.Here are a few places to start.  

Your friend would need to finance the purchase somehow (with cash primarily) or have a friend willing to negotiate a loan modification for them.   

It sounds like the seller did disclose to you in some form that HE made repairs/modifications to the units.

Both should require minimum modifications to lay down.

I am thinking a spreadsheet would accomplish most of the analysis part fairly easily with a much faster scenario modification time. 

Provide updated financials, get an updated appraisal, and sign a short renewal/modification agreement (there's usually a nominal renewal fee as well).

Fences can run over $10,000.If the tenants wanted to pay for the fence I would think the landlord would have to acaccommodate the request as disabled tenants are allowed their own expense to make modifications to the property.

Putting in some new fixtures and paint in a structure that is crumbling and will ultimately be bought by an investor who will tear out their modifications anyway is a waste if funds.

In some jurisdictions you are able to demand "vacant possession" of a property or individual rental unit under certain conditions (i.e. you or an immediate family member are to inhabit the unit, the building is going to be demolished, the building/unit will undergo a substantial renovation which necessitates it being empty, etc).The answer to your second question will depend upon location.  

Although I fully recognize this strain and can empathize 100%, I denied this request as I am aware of quite a bit of damage and unauthorized modifications that will require that security deposit to repair.I have tried to contact them to see how the new-house-hunting was coming along and mostly to get a good sense that they will in fact be moving out on or before 6/30.