It isn't like this a condominium where assessments are paying for common parts of the building like the roof, etc.Prior to this, I didn't have much experience serving on an HOA board and have therefore relied on the management company for their opinion on certain decisions. 

Budget overruns and unexpected delays seem to be a common theme in flips, so padding the budget by 20% makes a lot of sense.

Hard money is pretty common.

Would you be taking any pay loss from the job switch? 

Whereas if you and the other investors held ownership as TICs (Tenants in common) then you could sell your portion and do a 1031 of your portion while others did something else. 

It is common for investors to bring in additional signers, often referred to as credit enhancement.

I recognize there are other ways I could invest this cash (including another property) but I am being mindful of levering myself out too much in the current environment where job losses are more common in my industry (tech).

They have allowed me to quit my job as an Engineer. 

However, the average lifespan of companies is 10 to 18 years, so every private-sector job your tenants have will eventually disappear.

Being above four units, fairly common for the accepted offer needed before showings.