I'm really unsure of how to balance cashflow vs lower interest rates. 2) We plan on taking this $55k and leveraging it into being able to buy $275k - $366k (15-20% downpayment of the $55k) worth of loans to purchase properties.

If you are going after multifamily check out Freddie and Fannie small balance loan programs.

He called me and said he has $500 that he is giving me tomorrow and once his unemployment starts up he will pay me the $100 balance.

You need to be careful how you balance your write-offs to your income. 

It’s also an additional screening tool as they know up front that they aren’t getting keys until I confirm util are in their name and they won’t get a hookup without discharging an old account if there’s an unpaid balance.

As for paying back your HELOC there aren't many risks to having the balance out there.

Put laundromat on back burner for next year after apartment is stabilize open a HELOC on my primary residence and use combination with cash to purchase first small apartmentExit strategy use rent to pay HELOC monthly payments and then after 12 months refi property and pay off remaining balance of HELOCFEARS:1)When I open HELOC and pay for part of apartment what if I over leverage my HELOC.

At a guess at a 7 Cap makes valuation $314K.On the other hand, if he has kept rents stupidly low and you feel you can easily raise them to $800/mo, the potential upside value might be something like $800*12*12*.9=$103K, which at a 7 cap means you could achieve a value of $700K.

I received notice last night from tenants they will not be renewing lease and may not be able to come up with remaining balance do to work furlough. 

If you have other accounts that have good balances you can share that information with them as well as they want to make sure you have sufficient funds not only for the downpayment & mortgage payments, but also for reserves.