This would still give them a monthly cashflow, cure the capital gains tax requirement when sold [ check with CPA or tax attorney] and alleviate the maintenance / management issues that your parents currently have.   

I started hosting on Airbnb when I would go away on business or on vacation, and began to really enjoy the hosting experience and that high of making money from a passive investment.

Likely to get quicker gain, but without experience and low money down, your risk will shoot up exponentially.

I know EXACTLY where and how my numbers work and if I take longer than expected on construction and the sell (dispo- Sale)Let me ask you a question, if I loaned you 100k at 20% interest and you had no money out of pocket cause you used a gap lender at 9 %, and you still made $15k in 3-4 months OR MORE (I shoot for 15% profit), would you use the hard money loan to gain experience, knowledge and then leverage into better Interest rates the more you do?

Actively investing in 6 of these homes just to beat the passive broad stock market? 

If you are looking for passive income then use a company or agent that does full time management. 

I've run direct mail campaigns in several markets and it takes a lot of volume (3,000 letters minimum) and consistency (one touch per month) to gain any traction. 

This is a two-way interview, so have a short list of questions to ask the mentor (What books do you recommend I read to gain a better understanding?

@Jonathan Bock  The property has no liens so the passive income from a rental will be decent towards the new mortgage. 

What I am seeing as an agent it many of my clients are selling properties I got them and taking the gains.