Frankly, I think you are dreaming. The portables are use as much or more power than a roof unit to produce the same btus, so there is no gain there. Even if a smaller btu portable is used, it still has to run x hours/day to pruce the btu-hours to cool the place and will simply run lnger than a larger unit doing the same job.
RVs are horrible to heat or cool and require many more btu-hours per square ft than a house or apartment. RVs rapidly gain heat, especially in the sun, and have a much higher percentage f windows to wall area. Even a small RV needs 13k-15k btus of a/c and it will run most of the time during any hot day or in direct sun. Once night comes, the typically don't run all that much and power consumption is modest.
Add to that the loss of the very limited floor space and the nuisance of routing the portable ducts (in & out), and the whole idea is a loser.