Prior administrations changed labor laws to be unfavorable (I know someone that sold their peach orchard because of it).

The first and most important is that the QI must be in place prior to the closing of your sale.  

If the taxpayer used the property as a rental or vacation home prior to using it as his or her personal residence, then the amount of gain that can be excluded will be reduced for that period of “non-qualified use” (see IRC Sec. 121(b)(5).)

I had a few questions in terms of how the leases the tenants that were renting the unit out prior to me purchasing it works?

We ran the title and our DD prior to the auction and this issue did not come up.

Or do they know which ones can be approved prior to purchasing the SFR?

You should have inspected prior to closing and then refused to close if the tenants were not gone. 

If the property was vacant when you wrote up the purchase agreement then the prior owner is who you send any inquiries to.Check your purchase agreement, were any leases transferred or going to transfer to you the new owner for the property?

I believe I had actually done a prior introduction several years ago, but I was never in a "good place" to start actually investing.

For these situations, we subsidize the utility cost as that is our issue and not the tenant's issue (we try to be fair - we typically charge them the cost of their water usage from the period prior to the leak and we pay the overature).Good luck