You may possibly need the occupancy rate if it isn't already factored into the revenue estimate.If it's already factored in (assuming it likely is), next you'll need to factor the operating expenses so you can arrive at a net operating income.

It's possible tenants would fill basement with junk and leave it behind when they leave...

Rental portfolios would be a quicker way in - as you could possibly buy numerous properties in one transaction.  

Actually, it is possible do structure a 1031 Exchange on the sale of one or more relinquished properties and then using the proceeds through the 1031 Exchange to construct improvements on real property you already own.

They seem to be looking for a place urgently, possibly after a recent move. 

I live in Lexington county and would like to start local if possible.

If you can’t do a 1031 to a non-income tax state, figure out a year when you will have lower income and tax rates ar as low as possible.

Then rent the bigger home out using a property manager, allowing her to possibly cash flow and maintain that asset and let it continue to grow in value.Encourage her to consult with a CPA or tax attorney to explore the best strategy tailored to her situation.

Consider starting small by house hacking a single-family home, renting out rooms, or adding an ADU if possible.

Naturally your property must sell before you can take title to the new one, but nothing prevents you from getting it under contract and make the process as smooth as possible.