To solve this, I built a custom mobile app to handle rent payments and due dates because no other management software can handle the payment schedules or turnover.

If you are doing this for accounting purposes, maybe look into some kind of software like Quick Books.

Since then, I’ve been listening to BiggerPockets, On The Market, and Real Estate Rookie, and I’m currently reading The Multifamily Millionaire by Brandon Turner.A bit about myself:I'm a 31-year-old software engineer looking to become a long-term multifamily real estate investor (REI) and achieve FIRE (Financial Independence, Retire Early).

They also have tools for on boarding investors.There are property managements softwares to help with property/asset management.There are CRMs that help with capital raising and investor automations.I would not focus on automation right now, but on the business of multifamily.

I'm sure there are other software's out there, so just select one and go with it.

I suppose that’s a better set up than Zillow but I couldn’t imagine giving possibly 40% of my hard work to a software 

Do you use software?

Totally doable if that sounds like something you're willing to do.If you were looking to go that route, I'd recommend getting a Customer Relationship Management (CRM) software to keep track of leads and follow-ups.

Also using dynamic software pricing can help increase revenue. 

Apology for multiple posts - a forum software glitch apparently