Economies of scale sometimes push people to own more so that they can afford to do less.

It's an 8 unit, and they have had bed bugs before, and would throw their old furniture in the empty lot and burn it. 

I'm in the process of vetting lenders who can help me get started on my REI journey getting my first property/mortgage.Obviously, before I can buy I need to know what I'm pre-qualified to afford.

I don’t have a problem if you want to build a nice house; my main point is you are not getting a $400k heloc which is what your post implies.Here are my personal rules for  Building a personal residence: no more than 25% of income to payment, don’t go so custom That you can’t resell, Find out how long $500 k homes take to sell in your area; what percent of people in your area can afford it if you will sell in the future. $500 k would sit for too long in my area and I would not do more than $350k here, but that is just me.Good luck 

8-plexes would be easier to sell in the future since more buyers would be able to afford them.What is the optimal number of units where I can maximize economies of scale?

You don't want a tenant who can't afford the rent in the unit. 

We'll keep your rent unchanged so you can afford to stay here, but if we get voted out, those conservatives will raise your rent and you'll have to move. 

The mobile home was on the property and it is what I could afford to pay Cash for in the part of town I wanted to be in.

Small towns with more affordable properties for my budget. 

I work in pharmaceutical sales which affords me a decent pay and flexible schedule and I truly enjoy it so my properties will be passive income which will further support my family.My parents have a college rental at the University of Dayton which does very nice and I like the idea of that model as a fairly safe and reliable source of passive income.