Most sellers are liquidating to achieve a monthly income.

It’s off market and the owner wants to sell because he’s retiring and wants to liquidate his investments.

Right now, with the CC payments, you're about break even, maybe a little positive on cashflow so there's no reason to liquidate, there's time to come up with a plan.

The shower is small and the spray faces the door which gets the floor wet.

Just diversify your portfolio a bit.Then youd be able to live off the cashflow from your 3 other 4plexs, since you have no living expenses, yes you wouldnt be rich or anyhting but you could live a comfortable frugal life without having to work.This way you'd have money thats fairly liquid as well in your TFSA, in case you had to do any repairs or to account for miscellaneous problems that could occur, and in the very worst case you could do a HELOC  to pay for any major major disaters that could occur with all the equity youve created in your home by using the BRRRR investment strategy.These numbers are just examples, however its not unheard of to BRRRR a property and actually come out with more cash than it cost for the DP and Renos, which would help acquire even more property.And if you can get 50K into your TFSA and get a return of 8% from a dividend then thats an additional $350/month roughly, all while living for free. 

If you do not have experience or significant liquidity most lenders are going to shy away.

You need to know if the heloc is interest only as well (many are).HELOC is great to have, but you're right it's more beneficial for liquidity needs rather than long term debt service. those mortgage terms sound good!

I currently have no real savings outside of my company's 401(K) and only a small amount of liquid stocks and cryptocurrency that I could sell.One of the private equity firms founders suggested flipping a couple multi-family or single-family homes in order to pay off my debts and build a war chest to be used as a down payment on a rental property (I thought this sounds like a good idea). 

IE. retirement age, needed income, wanted income, liquidation plan, cash reserves plan, lendability plan....Danny Webber, MBA, Broker- Home Simple of TexasOwner- Investor Depot.comOwner- The Texas Builder.com

At your age/income level, you should be 100% focused on learning about investing and aggressively investing your money into liquid assets.