It probably doesn't include income from the 5th or 6th unit if it's supposed to be a loan for 4 units right?

Maybe they mean your net, net income? 

Could the rental income justify the price?

The city's strong rental market driven by a growing population ensures a steady income stream and with affordability as well as a median home price below the national average, Cleveland stands out as an attractive option for those seeking a promising return.

You need income of $6300 or more if you have a car loan/student loans/credit cards.

I offer them a lump sum and monthly income.  

I am starting from ground zero, with no prior background or capital to invest, but with a strong desire to create passive income for my family.I currently work as a middle school teacher in California, and while I love my profession, I have a strong desire to explore avenues that could potentially provide financial stability and additional income streams.

It’s crucial to acquaint yourself with FIRPTA regulations, which mandate income tax withholding on the disposition of U.S. real property interests by foreign individuals.

Then you boogie to find a buyer and its their EMD that goes into escrow to secure the deal. 

U want your parents to talk to their CPA FIRST.. if they go the development route they are now ( depending on the amount of units) creating inventory.. which will be taxed at ordinary income rates ( very HIGH)if they just sell they can 1031  and move on to something else.. many times when you run the math consider the risks of a partnership.. the sale of the land is far better than thinking your going to make some profit..