I’m originally from Plano and always looking to get back home with a 20+ units complex!

Storage is not rocket science by any stretch but if you are new to this, it might be advisable to master that before adding to the complexity.

I have an apartment complex in a college town that I picked up late last year.

Here's an idea @David Sweatman:If you have a 100k to invest then your personal residence is probably paid off.If you have good credit, use the good credit to get a HELOC at a great rate.Then use the money from your HELOC (and the 100k) as a down payment for a 20-40 unit apartment complex or commercial building.If you have an IRA with more 50k - you should consider using a self-directed IRA to invest that money in real estate too.

my answer is noEconomies of scale works better as you go bigger, this is why developers are building tons of large unit volume buildings in the area and very few duplex/triplex/quadplex or small complexes.

I'm doing some preliminary work on purchasing a condo in Mobile, AL, but the complex itself is a bit shoddy.

We are also considering just doing an umbrella policy instead depending on the complexity of doing the LLCs. 

I lived in this apartment complex 12 yrs ago. 5 rental units in top of bldg and 4 stores on bottom of bldg.

Determine on your own, with your family or with someone you trust which elements of the home each of you will check out during the tour and stick with the plan no matter how terrific the home looks to the naked eye.All homes are complex no matter how big or small, old or new.

I have been looking for an IRR excel calculator but they all seem too complex and I'm not confident with them.