If I were afraid of paying that extra amount per month needed to keep the 15 year house mortgage going(assuming I can rent it) in addition to putting down 20% for a new owner occupied property, I think my best options would be:1.

I have a small amount of extra cash and want to look into investing in real estate!

Maybe an extra $100 or $150.

If the extra LED sign, or paint, or white boards, or gadgets can produce the return you are looking for, then you have a winner.

Just the possibility to live for free is very appealing and make extra cash from renting the 3rd unit  (if it`s 3plex ) is very sweet.

Seems like pulling out an extra$10-20K would be a great step into your next property without affecting your cash flow too muckken

And I'm living for free so that's an extra 1500/mo in my pocket until I can afford to get my second property.

My heart wants to do it, but I would appreciate any extra opinion.

Extra expenses will be sure to come up; I just want to be sure i'm in a good spot before they do so I can handle them! 

If you HAVE more than 25% to play with (on top of the necessary extra reserves you need anyway), use it towards ANOTHER deal!