As far as major issues- honestly nothing was insurmountable - the biggest issues that I've come across has mostly been deferred maintenance from previous owners and having to put more money than I originally planned in at the start, but honestly I'm seeing that money in area appreciation and with the excellent cash flow (For example I paid about 65k for my duplex and now I'm getting 1200 a month for it)We had some wood rot which was a little expensive to fix, but it was fine.

The tenant has almost an insurmountable amount of work to provide for that family:  provide an income, cook, clean, shop, get the kids to school, etc...   

Nothing is insurmountable!

SO many things go wrong, and by wrong I'm not talking insurmountable, but those things that cause delays. 

I've run some numbers on some Trenton (and New Brunswick and Newark) properties, and while it's not insurmountable by any means, it certainly makes it more difficult!

But I my limited experience with lenders over the past 12 months is that they aren’t exactly throwing out insurmountable or unreasonable roadblocks when it comes to lending.

@Scott Hollister should be able to provide insurmountable amounts of value on this one... ;)

Not insurmountable but adds cost.

Now, he relies on his metrics, and is able to make more rational decisions.IMHO, the worst thing you could do is view your 3-4 years abroad as an insurmountable obstacle in expanding your portfolio - it's not at all the case. 

This can be overcome with a little self development, and so is not an insurmountable obstacle.