I've been house hacking my place (I rent out a 3-bed 2-bath residence and live in a small in-law unit in the back) for just about 3 years and have been setting aside money each month for my reserve fund.

In your case looking to larger assets where you can effeciently cost segregate to gather bonus depreciation would be a smart move.Appreciation - Where in the country is the asset class you like growing or going to be growingAmortization of the loan - What sector or even region if you look locally for funding, is going to offer the most favorable lending so that less goes to interest expense and more to pay down of principle.Have fun with a spread sheet comparing these 4 returns from your investment with the type and location of assets you find attractive. 

They will have requirements on how you can document the transfer of funds.

Without knowing your age, I like the idea of pushing additional savings into good, no load index funds (I like Vanguard's S&P index but there are plenty of others) through a Roth if you're young enough, leave the rental portfolio as is and pay the debt down to nothing, since you're not inclined to really work at growing that end of it. 

Flexibility in Financing: Cross collateral loans can provide flexibility in funding different projects or investments without needing to secure additional loans.Cons:1.

BRRRR is a learning curve and most lenders aren't looking to fund 100% of a project for a newbie. 

Things that cause delays are many sponsors maybe 1-3 people and they outsource their investor relations so the first person you contact is not a member of the company but a call servicePersonally I would not invest in a fund / syndication that has a call service on IR side as if things go wrong you will never hear from them.

There is a Fund of Funds involved.  

If you are able to network with someone that can give you consistent deal flow and partner with people that will provide the funding you will be in really good shape.

Or, he could rent his home and use the rental income from it to fund a mortgage on the new home.