It's a split-level, and they turned the two-car garage into an "apartment" area; they removed the garage doors, sided the exterior walls to match the rest of the house, insulated, drywalled, & painted the interior walls, etc.

It is a fourplex, so we are going to be redoing 4 bathrooms, 6 bedrooms, 4 kitches, floors, mini splits AC added, replacing plumbing, roof, repainting the exterior/interior. 

@Joshua Messinger , yes, the interior is outdated. these are 2 bedroom units, one side is vacant, the other has a long term tenant that wants to stay and is paying $600, comps are between $700-900. 

If you have central HVAC system, you typically remove the vent grille in each room, then the interior of the duct can be cleaned all the way back to the main HVAC unit with a series of large "bottle" brushes on extensions, rotated by some type of motor depending on size.

Line item each element...roof, siding, exterior paint, interior cabinetry, flooring, interior paint, plumbing waste and supply lines, etc. then google "construction useful life" to find charts that give you an estimated life of each element.

I am already planning on renovating the kitchen, bathroom; I am just wondering if it is worth going through the process to design the interior as well.

Personally I'd try to working interior remodeling/finishing jobs.

My husband & I updated the interior of the home and hired help to renovate the entire exterior space.

Purchase price: $175,000 Cash invested: $35,000 Sale price: $278,000 Move in ready, new carpet, appliances, fixtures, ceiling fans, interior paint.

Listings with reduced prices that don't sell tend to be a combination of what Bill said: too high to begin with and buyer sentiment (wants to lowball, thinks you're overly desperate to sell, etc).This is now the time to re-evaluate the curb appeal, interior staging, listing presentation appeal, increase open houses, and consider a upfront credit to buyer to re-attract customers.