What I have found with a truly dependable PM (very hard to find what I have I think) all those problems go away, plus I have a moderately good cash flow generator, quite strong underlying appreciation and very good tax benefits.

Rates have gone down since my mortgage so I'm currently refinancing my house and I save $100 a month on payment (it will take 4.5 years to see the benefit) which I plan to apply to my HELOC.Ideally, I would like to downsize considerably and buy another primary home and rent out my current house to which I think I could gain a +$200 cashflow to also go towards my HELOC. 

Larger than that is when you really start seeing benefits with efficiencies.The 1-2%/50% "rules" are still applicable to multifamily properties for quickly judging expenses before digging more.

Referral benefits? 

On one hand, having the mortgage interest deduction against the rental income seems like a positive (but then closing costs seem to negate that benefit.)

You can usually offer more to get the deal done compared to flip/rehab prices and the benefits/cash flow comes on the terms.

Each have their benefits and some have some very high costs in regards to up front capital unless you put a Heloc down, do Hard Money Loans, or borrow from family.

The new lease between us was also a benefit to her because then she had instructions on where to send her payment portion. 

So your "Gross income net of mortgage" is $550/month which is 26.4% gross income over your $25k investment. so you can clearly see there's a benefit in leverage, NOT to mention you also get tax advantage because you get to reduce your income by interest expense so in the first year you are probably reducing your taxable income by $5000 or so...

There is a nice tax benefit to occupying a house for 2 years out of 5 for civilians and and extended period for military on orders (as both me and my husband were).