Would it be just as profitable to sell their building/land and not build?

They are looking to sell and would be subject to FIRPTA tax. 

Should we risk renting or just sell?

We prefer to have tenants on yearly written leases, unless we are looking to sell the property or have other plans and may do extensions of 6 months and one day if tenants are planning to relocate, purchase a home, etc,  and cannot commit to a 12 month lease.

If good it will sell in a day, Good luck 

First thing I would consider starting out is identifying which specific neighborhoods within those cities.

Then I’d sell the homes and switch to just land rent. 

I design affordable custom websites for small businesses, my designs specifically focus on getting the highest Google PageSpeed scores possible (example) which boosts their ability to rank in search engines and making sure their site includes at least 2 content silo pages that rank for specific keywords (ie "sell my house in Atlanta, GA"). 

As a result, I received early notice he was looking to sell.

The plan was to sell the house so I moved into a condo in August of 2019.