It 12 years, assuming you make no extra payments, you'll have a paid off condo that cash flows a lot better. 

Not when there are so many alternative methods of engagement towards resolve of which past clients have appreciated.

After they asses what all needs replacing or what they feel needs replacing they'll submit to you what they're willing to cover and deductibles and payments etc. 

Last year, on my 9 properties I had negative cash flow after accounting for mortgage payments, etc.

Publication 15, Employer's Tax Guide, says only this much:...Payments for the services of a child under age 18 who works for their parent in a trade or business aren't subject to social security andMedicare taxes...No definition, and IRS publications are not really law anyway.

I don't plan on sticking to one method of investing however I do realize that some investors start with Single family and grow into multi-family.

I started by saving up for a down payment which was 5% for the first "second home" property in 2004, then 10% on the next few. 

The issue is, I'm not sure if my income will be enough to cover 2x the monthly mortgage payment that most loans require.

Poor rental payment history is a common cause for non renewal. 

This method is particularly relevant if you're in a market with high rental demand.Many property owners have found that adding an ADU significantly increases their property's market value and appeal.