Seriously, grime and dust and dirt can make a place feel pretty undesirable - you don't even always notice it when it's there, but you will notice it when it's gone because the place will just look, feel, and smell nicer.- On that same note, one of the other most important things is also to make the place feel light and bright.

If the area is in a geographically undesireable area or blighted neighborhood that is slowly declining which many communities in the Country are it may not be a very good investment.

Normal life changes for family units still apply, but vacancy is less than 10% and due to waiting lists, quickly rented if new vouchers are authorized.It's the landlord's responsibility to screen tenants, you can certainly have quality tenants in Sec 8, if you preceive this group as being undesirable, it's not the socio-economic factor as much as the lack of due diligence by the owner/manager.

And it we are, on none rent control unit, can we just raise the rent really high so the undesired tenants would go away?

Just find the most crime ridden,  undesirable area with frigid storms in the winter and mosquitos the size of small birds in the summer and invest there. 

As long as it's undesirable there may be appreciation in small pockets (i.e taking a distressed property & flipping it) but the area in general will not appreciate.  

It was a nice house but needed updating and repairs and it was in an undesirable area.

The constant drumbeat against landlords in CA has made it a really undesirable place to own over the long term (which is why I stopped buying rentals here a few years ago and have been a net seller). 

@Daniel Hansen, Here's some that a small-time rental portfolio manager has in mind for systems.Rent Collection: Automate through ACH or Direct Deposit, as opposed to drive to the homes and collect rent checksMaintenance: Have a handyman "guy" or a crew that you can text and schedule, as opposed to run around to fix toiletsNeighborhood Watch: Make friends with the neighbors and have them alert you when there's undesirable events etc. going around the propertyProperty Management: If you choose this, have several property managers that you constantly keeping tabs on to help with management.

We do a quick 5 minute-8 question telephone screening that weeds out most of the undesirables and gives me valuable information.