I'm also working on a Google Data Analyst certification to bring in some extra income while I'm home with our 19-month-old daughter.I'm still pretty new to this, though, and I'm not sure where to start or if I'm on the right track.

Same income, same credit, DTI ratio, underwriting requirements.

I am currently enjoying my 1k monthly income with no debt, and I am nervous about leveraging.  

You can have multiple conventional mortgages and have a great credit score as long as you don't pay late or get too close to the maximum debt to income ratio.

Did a 125k upgrade to unit, but now need to make income.  

Affordability is no more that $4500 per month  morthage/taxes insurance. 

Screen them as you normally would - does their income substantiate their portion of the rent +/- a little for changes in what the housing authority will pay out?

Quote from @Chris Seveney: @Jay HinrichsWhen I looked into it - I viewed it more as those who teach infinite banking etc (note that is not what tardus does - they teach what they call income snowball)Similar to infinite banking - it’s a strategy and you pay to learn the strategy - but whatever you invest in is up to you.

@Allen Harris  Yes.. there is that there is the cost of the tax return ( that can be cheap with one prop) but its still something like 1 months cash flow then the income tax is probably another month.. then add in a trip or two there and you have wiped out 4 to 6 months of cash flow compared to what you could do right at home. and Lord knows there are plenty of low end homes in Memphis that rival these..

Quote from @V.G Jason: Organize taxes and eat better.