Double check any cap ex you might have coming in the next year or more there so you can plan to set that aside (boilers, roofs, etc).

Is there anything wrong with me (legaly - he also bought the same stock and made 5x more than me) and is willing to take on cap gains as a thank you for me.

Cap rate is a good metric.... as long as you know if all the expenses are in the scenarios.

During that time I've often described the multifamily market as a traffic collision at a 4-way intersection where you had (lack of or negative) rent growth coming from one direction, and from the other directions: cap rates, expenses, and interest rates. 

Let's see: You sell one property, and to avoid paying cap gains tax, you then reinvest those profits within 45 days into a larger "like kind" property.

Is this structure standard, though, in terms of capping investor returns at 12%?  

If one or more units are vacant, the remaining units often don’t provide enough cash flow to cover expenses, making it harder to meet operating costs.Maintenance costs: A fourplex comes with four times the appliances, plumbing, HVAC systems, and other components to maintain, leading to significantly higher repair and maintenance expenses than single-family homes.If you want to see the detailed calculation, read this BP blog - More Units Doesn’t Mean More Money—Why a Single-Family Home Can Beat a Fourplex.Resale value: Multi-family properties have a limited buyer pool—mainly investors—who base their offers on CAP rates.

That's what keeps investors like yourself holding on because the cash flow is non existent between management fees and cap ex which may not present itself in year 1, but when it does, its crushing in these lower price point properties.

One posted about buying a cheap quad,  i used her bumbers provided and my maintenance/cap ex to show negative $600/month.  

Cap Rae 6.4%  Love to hear from you.