As such - I'd highly recommend you check out "The Book on Estimating Rehab Costs" that BiggerPockets just released along side "the Book on Flipping Houses" - you may want to check those out here - they are both excellent.

Subsequently, you would invest the borrowed funds alongside your solo 401(k) under a tenancy in common transaction (TIC).

Also providing money to back additional investments.Long term goal is to grow to about 20+ units to provide enough income for early retirement alongside my company paid pension. 

This is one large water heater tank (75gal)  in the basement, alongside a boiler that feeds the radiators throughout.

I would definitely start by writing down your goals on paper along side with a list of niches and strategies. 

I'm currently 55, and I did the rehabs myself --some solo or working alongside hired labor(cleaning, painting, installing counters, flooring)  some tasks I had done by skilled tradesmen (toilet removal, heater installation, drywall).

The second attempt right before signing for my loan the numbers didn’t make sense any more, and a hiccup with electrical came up.

However, because this is primarily a cash flow investment, it seems fair that I could take income alongside the silent partner (once we reach a certain percentage of return). 

Got it.Since the complex isn't providing the cleaners, you could always look into if there's a local cleaning service that also provides linens or works alongside a linen service.  

If you’re on a month to month lease, typically your landlord only needs to give 30-60 days’ notice.Moving residences costs money, and you’ll need to find a deposit plus up to two months’ rent in advance for a new property, alongside the fees listed below.