Therefore setup a good filing systemGet a good answering system…Vonage Phone is one good exampleStamps.com is great for keeping track of letters you send your tenants.QuickBooks is a Landlords best friend.

@Shmuel Waldman can direct mail be me seeing a house while out cold calling.. writing a letter on the spot and dropping it in there mail box?

Assuming you sent the non-renewal letters via Certified Mail, then that receipt serves as your record of delivery/notice (even if the tenant claims he never received it) The clock would be ticking from that date of delivery or attempted delivery.

Also, get construction loans that convert into a mortgage so a worst case scenario you can make payments instead of worrying about a balloon payment. 

Once you have removed the doubt of a previous owner wanting to get their property back by saying the county didn't handle things to the letter of the law, then you can get title insurance protecting your 100% ownership then sell like any other property.If you have a lot of old owners or bigger problems the the quit claim deeds from the people you can find will help speed up a Quiet Title Action.

@Adam Philpot Sometimes thes letter designations are limiting and misleading.

You can still get a loan on it but it means you have to get a commercial loan (usually 5-10yr maturity with balloon, 25-30yr amortization schedule though). 

Once you start getting into the commercial world you tend to see more 'creative' options but one commonality I hear a lot of is that a 5 year balloon term or at least matching a market interest rate is common in commercial type lending. 

I keep getting letters from the sewer department this year that my tenant is always behind on his sewer bill.

When lease renewal time comes for our tenants, we send a form letter on our letterhead with 2-3 renewal options.