We're turning a basement back into a garage

At Arch Buyers, we recently purchased a new 4-family property in Saint Louis County. 

The building has a spacious basement garage that the previous owner only used for storage. We can add a lot of value by turning it back into a functional garage, providing off-street parking.

The garage doors need to be replaced

The garage door was built on a 90 degree angle, basically with two side-sliding doors that both need to be manually pulled back to enter the garage. Inside the garage, angles are still tricky, since there are load-bearing beams that have to be avoided when driving in.

The opening was built when cars were a lot smaller, so it's a tight fit -- but just big enough to work. 

Which garage door is better: Side-Sliding or Overhead? 

So we're planning to replace the existing, decades-old doors. We want to install a modern remote-opening door, but have the following questions: 

1. In general, which garage door is better: side-sliding or overhead? 
2. If we install an overhead door, would it be realistic to build a door in between the two ends of the current opening (cutting across the 90 degree bend)? 
3. What considerations -- cost, difficulty of installation, lifespan -- should we keep in mind? 

We've undertaken some substantial rehab projects in the past, but garage doors are a completely new foray -- we greatly appreciate your Bigger Pockets advice!