The process starts with setting up a support network of professionals who can help you analyze undeveloped property; as there are significantly more unknown factors in play with vacant land lots than with those which have already seen development.

I am sure some people are are confortable taking a very old house rebuild, but the risk of unknowns could quickly eat up your profit.I recently finished a 1965 rebuild, and by the time I was done, spent way more than I originally anticipated (it was my first old flip) and if I had to do it again, I would have razed it, and built new. 

Your gut is probably right but regardless, you don't want to boot a good paying tenant just because of unknowns.

@Darius OglozaI think you may be right, there is just too many unknowns.

If so let the city do the dirty work.If they were permitted inside by the last resident consider the following.Serve a 5 day notice to the last tenant of record and "Any and all known or unknown residents of" ________________________.

Title insurance is Not for any problems found, it's for unknown problems.

Don't want to invest in tier 3 (unknown/unheard/middle of nowhere) cities.  2.

There are a lot of unknowns here.

Remember, your property taxes are the product of your assessment multiplied by the tax rate, which is unknown.

It can cost upwards of $5,000 if there are unknown or unfindable parties or heirs.