Retire Early with Real Estate- Chad CarsonThis book details many investors who have retired or supplement their retirement with real estate. 

You also back into it by taking the known ROI you require and multiply that by the spend, this will tell you how much you need in a rent bump to justify it.Me personally, I use between 20-25% ROI as my threshold.Another thought to this is if you can do this for 20 units and do secure the $100 rent bump then you just made the property worth 400k more assuming a 6 CAP or 300k if using an 8 CAP. this will help when time to sell or do a cash-out refi or supplemental loan.    

Looking for cash flowing buy and hold real estate that will supplement retirement income.

Also, to supplement what @Brent Crosby said, it's not timing the market, it's time in the market that matters.

We hope to learn how to invest in real estate in a largely passive way in order to generate cashflow to supplement our regular (or rather, "irregular") income.

@Gerardo EscutiaI would tell them to get a window AC unit to supplement if they need it lower.

Decided to get into rental real estate to supplement my advertising sales job.   

I am wanting to get into real estate to supplement my w2 income. 

I am currently in the engineering side of the automotive manufacturing world, but my goal is to pursue real estate investing as a supplemental income and potentially future career.

I couldn't have done this without the bigger pockets community, and supplemental materials provided to me by this site and its members.