power should not be an issue . he should have axx to building power at the top to power the converter and power at the point when looking to distribute the signal.
Ps those inline amps are not good for what your trying to do.
If your looking to go on the cheap see what your options are . Coax systems $900-1300 in hardware not labor or plenum. Fiber $2k+ but you can push it verry far without issues.
Will the building let you use anything other then plenum cable? Local codes and insureance issues.
Can the Existing conduit take RG6/11 ? Can you get 5-6lines through it? What other signals are going though the building CATV,Microwave, Ect.. This will help you out in many many ways.