Security Deposits are the biggest point of contention because clearly they need the money.  

The biggest hindrance for me is that my current job pays well and anything I am finding that is closer to me and in the real estate industry is paying 30% less than I am making now. 

@Rob BeardsleyHere is a real life example.Around 2004, I bought a property for approximately $890k in Brooklyn, NY and had very little monthly cash flow.TODAY, That property is now worth close to $3 Million and Cash Flows around $5k per month.I'd like to Contrast that with a friend of mine, Steve.Steve bought approximately the same Value of properties, but for Cash Flow in Bristol, CT.He has been making $1k Cash Flow for the past 13 years.The Value of his properties, which was similar to mine when I first bought, bearly move up, probably around $100k more.His Cash Flow never really grew, mostly because the Property Taxes kept climbing with any increase in rent in his area in Bristol.The Biggest problem that Steve had was that he lived in NYC.In 2004, his apt that he rented was renting for $2,000 per month.

Finding great property management is the biggest hurdle.

Price was the biggest factor for my 20 units.  

By biggest goal initially is to figure out what niche will serve me best.

if I had 300 doors and was going to sell only 12-20 I would bet its the bottom 12-20 performers, the ones with the biggest headaches etc. 

The biggest problem with her and others is that they allow bad tenants a measure of validation. 

@Carol Bahou If the low down payment is your biggest barrier to entry, than I'd suggest you think about your issue in a different way. 

The biggest thing we learned is that the tenants are young and not use to being on their own.