We've been honing in on a pretty good development/investment formula that is working for us where we buy an existing single or multi-family house that can be improved or easily split into smaller units, and then we also add small new construction units to the property (townhomes or duplexes or cottages) and, generally, we rent them all out (though we have sold a couple of single family rehabs and we may sell the units in our next big project...

Not on Redfin or the mls.

In addition to this, I own a property in Plantation, Florida, where I’m exploring the potential to add apartments or convert it into a multifamily unit.

If you do not have any prior experience I would hire a manageable property by a manage company that has section 8 experience or if you are going to manage them, I would get it in a "C" location or better.  

Income from a trade or business where a taxpayer doesn’t materially participate.2.

Roth IRAs offer tax-free growth, meaning that rental income, appreciation, and gains generated within the account are not taxed, but you cannot take advantage of deductions like depreciation or mortgage interest on your personal tax return.

I assume the seller isn’t selling their $350k home for $50k…If the buyer gets a loan or pays cash for $350k then it’s just a traditional sale. 

What does scare me are hidden fees or liens on the property I cannot currently see. 

Choices= bad, horrible or complete nightmare (paraphrasing). 

Mostly that means a limit in the number of units you own, whether or not you broker it yourself or through an agent.