Looking at City owned properties now and the killer is the standing tax lien that needs paid off...  

Be concerned of the age of home (post 1974 is better) and maintenance is usually the killer I see.

Got sooo pissed off that one weekend I was determined to find a new landscaping guy... so I pulled up all the rehab properties in my area and drove down their to check out their land scapping... strangly enough this one group had killer grass... so i sent my runner to stay infront of the house until the gardner comes...

That is something that would discourage most people, and i agree that it is a cashflow killer, but there is no other product that is so easy to obtain, with so little down, at such a good rate. 

And keep in mind that an FHA appraisal is going to attach to that house for 6 months.On the buy side I actually like purchasing a FSBO for a client because I know they are going to get a killer deal after the price is adjusted after the appraisal, as well as being able to negotiate absurd seller subsidies or repairs after an inspection since the seller doesnt know what is customary in the market.

NJ property taxes are a killer, and Trenton is generally a terrible city known for its high crime. 

I hadn't really thought much about being able to cater to all sorts of buyers and sellers but being able to merge being a Realtor with wholesaling could be a killer combination. 

@Benjamin SchultzFrom a financing perspective POHs can be deal killers. 

My issue is my debt to income ratio; daycare is killer.

My wife and I lived in a 1br condo for a few years before moving out and making that into an additional rental for us.I'm biased of course, but I think meeting with an investment-minded real estate agent is a killer idea. ;)Good luck!