If they don't comply, which they likely won't, give them notice that their tenancy is not being renewed and they have 30 days to be out.We have gotten rid of multiple undesirable tenants by not renewing month to month tenancy. 

Threatening to sue me for something frivolous will get the tenant on my undesired list and has yet to result in an actual suit. 

He inherited a bit of a mess from the previous owner (bedbugs, undesirable tenants, and deferred maintenance), but we're getting things straightened out. 

A 401k loan has some risks...get layed off and have to pay it back or pay the 10% early penalty as well as income taxes if you cannot.A self-directed IRA is the typical retirement savings vehicle to invest in RE but it has undesireable attributes too.If you are young, you could diversify internationally or dip a little into emerging markets....they are not as highly valued.

In the few days I followed, I saw 10 to 15 properties sold to 3rd party bidders (daily), but the majority of those were either in undesirable areas or sold at a price that left little to no margin for an investor.  

The entire area should be leveled in order to drive out the undesireables and the problems they bring with them.

We take this very seriously as this defrays having undesirable occupants.

If I raise the rents, I might run into the unfortunate situation of having high turn over within a short time and that will put me in an undesirable financial situation,especially when I am pouring in large amounts of cash into rehab. 

@Charmaine M. marked rembert does raid some good points but for a buy and hold if you wait and search for the right deal you could do very will in Jamaica even south ozone park simply because I remember before I moved out of nyc I had friends living in what was affordable but undesirable areas like bush wick east New York and Canarsie....

I read somewhere that it is often undesirable to deal with properties represented by a broker when wholesaling.