Install vinyl plank floors and paint the walls grey.

In reality what happens is you end up paying more for a "clean house" but because you are doing a flip people want new mechanicals (central air, 200 amp electric, pvc plumbing stack) so you end up doing a full gut or larger rehab then simple cosmetics and now your returns have shrunk.In your situation for your first investment I would be ok with a smaller return because of the experience gained, but for the next look for larger profit.

Trying to estimate total cost to install new vinyl plank flooring throughout.

Furthermore, understanding the resident characteristics allows me to measure the target market and modify my investment strategy accordingly.Inspection ChecklistSituations vary from one property to the next, but here is an on-site inspection checklist to get you started:Interior Units:Inspect vacant units, including one of each finish out type (Classic, Reno, etc.).Check all down units.Inspect one unit from each unit mix.Exteriors:Landscape:Look for overgrown bushes.Identify trees that need trimming (no branches hanging over the roof).Take pictures of the following:Curb appeal on all sides facing the street.Landscape around the office and amenities.Overgrown bushes or trees.Any dead landscape.Areas that may need sod or mulch.Assess drainage:Ensure water flows away from building foundations.Check slope, gutters, downspouts, surface drains, French drains, etc.Exterior Walls:Determine the existing material (wood, vinyl, Hardie, brick, stone).Assess the condition of the walls.Note if painting is required.Take pictures of each building, including building number, each elevation (clockwise), and any breezeways or niches.Windows:Evaluate the condition of existing windows.Consider whether solar screens should be installed.Roof:Identify the type of roof.Assess its condition and age.Parking Lot:Check for potholes.Assess the need for restriping.Note whether the parking lot is concrete or asphalt.Evaluate drainage issues.Walkway:Look for tripping hazards.Assess drainage issues.Foundation/Gutters:Inspect for cracks in the brick.Check for separation in corners from fascia and trim boards.Evaluate drainage and identify poor drainage areas.Amenities:Identify possible improvements.Consider adjustments or additions that can enhance amenities.Talk to the Staff:Maintenance: Inquire about the physical condition.Office: Discuss current residents, delinquency, and potential changes to add value.Assess whether rents are too high or too low.Confirm rents and what is included/not included.Confirm other sources of income and associated charges.Confirm occupancy, pre-release, and vacancy numbers.Note: Maintain professionalism and avoid insulting the owner or broker, regardless of the property's condition.Keep in mind that investing in real estate is like solving a puzzle—you need all the pieces to see the big picture.

At the same time, all the single pane aluminum framed windows were replaced for double pane vinyl windows.

The discharge side of a sewage ejector should be PVC (plastic) pipe that is designed for high pressure. 

Run  some 220V wiring in pvc underground (licensed electrician) to power a good pump if you have space/amperage reserve in your electrical panel. 220V requires less current to run than a 120V for the same power, so it's more efficient.This guy has a lot of good videos on diy yard drainage systems.

➡️ Are the sewer lines made of cast iron or PVC?

But I would recommend luxury vinyl plank (SPC - stone composite) with a high wear layer, or wood look ceramic tile.

Consider vinyl trim in the future as it can withstand moisture.