Whichever marketing method you choose (mailing, cold calling, online ads, etc) Consistency is key!!

Whichever way you decide to go, just have your team (plumbers, electricians, handyman, roofer, yardman, carpenter, etc.) in place.

They get in, do the repairs, and put them back on the market for rent or sale, whichever you are looking to do.

Omar,if your brother owes more than the house is worth on the marketplace,you need to negotiate a short sale with the bank.After two long years,they are probably willing to listen to a short sale proposal.Your brothers credit is probably already destroyed so it's not gonna hurt him anymore than the pain he has already self inflicted on himself.If he refuses to deal with the bank himself,you need him put you on the title or give you power of attorney to handle the transaction yourself (whichever doesn't harm your personal credit).It honestly might be easier just to let the bank take it now and be done with it.Neither you nor he will get a penny of profit at this point.

Good luck with whichever decision you make. 

Either to clean it up or move on whichever becomes the most prudent choice.

My agent has told the Seller's agent that the Seller could even choose whichever unit to request to vacate.Does anyone have any advice or creative ideas for approaches we could take to either: 1) get the Seller to comply with serving 60 notice to vacate to one of the units or 2) Any other loans with low down payment options for a 4 unit property?

I'd start by making a call to the planning department of whichever county your property falls under to find out what it would take to start that process.  

Basically, whichever makes you happiest.

SACRAMENTO —The Contractors State License Board (CSLB) is alerting California consumers who are considering hiring a painter, landscaper – or any other type of construction contractor – that it is illegal to ask for or accept a down payment of more than 10 percent of the total home improvement contract price or $1,000, whichever is less.