Flooring suggestion for uneven concrete floor

[Larry Turowski]

I'm beginning to remodel units in a small complex with concrete floors.  Here is a before picture of one of the units.  They all were kinda ugly and had rugs which would require constant cleaning or replacement:

Here is an after, with vinyl plank flooring: 

It looks a lot better, but this particular unit had a pretty even floor.   There are some that slope down a bit at one point, maybe where a wall used to be.

Any suggestions on durable, attractive, but not too expensive flooring?  I've considered linoleum.