We have a few custom builders who put out maybe 10-20 a year, mostly high end

Everyone is different and until you try the first you will have no idea if you want to dedicate the next 5 years of your life to it.What happens if you get the first one and the following happens1.

As Min Zhang suggested, making sure you have a reliable property management company is key and can ensure you aren't dedicating any extra time to taking care of this asset when you already have a job with demanding hours.

If the product/contract/service I offer is not suitable to you then I don't want you to be my customer.

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.

The project seeks zoning approval to build over 59 million square feet of space dedicated to quantum research, offices, and cryogenic facilities.This ambitious project dubbed the Illinois Quantum and Microelectronics Park, is backed by both state and federal agencies.

As soon as you start discussing your business practice and strategies with your customers (tenants), then all bets are off and you run the risk of Fair Housing violations. 

The long term goal is to do custom homes, starting with spec builds.

REI Central and CHS Circle have dedicated facebook pages as well.

They offer flexibility in design and can be customized to include a business space.Shipping container homes: While trendy, these can be challenging for mixed-use (residential/commercial) purposes due to zoning and building code issues in many areas.