I have a buy and hold strategy and have left over materials like paint and laminate flooring.

The flooring in the average elementary school is Armstrong Vinyl Composition Title Flooring.  

You don't need to worry too much about that.Benefits of assigning: You get your fee and walk away, Super easy and clean for youBenefits of double close: Your investor will never know what you are actually making on the deal

I’m confident in my ability to do a lot of the work on the house If need be however I don’t own all the proper tools to do so and there is stIll a lot of steps that go into flipping I don’t have experience in (I.e. tile, flooring, sheet rock) due to previous jobs I have relationships with a large multitude of contractors, electricians, plumbers, carpenters etc I don’t have a specific house picked out at the moment however I do have several target neighborhoods I’ve been keeping an eye on.

So it's like someone slipped and fell on your property after a snowstorm and it's "you mean you  didn't get someone to clean up the snow?" 

What is the ballpark cost to build a multistorey building (say 3-5 floors) vs. a single story building?

Stainless steel, biggest kitchen faucet, shower heads.Granite or quarter counter top are expected to bring in a higher price, flooring.

Like the roof, A/C, type of electrical wiring, water heaters, garage existence and attached or detached, fencing, windows,  flooring type throughout, concrete slab or pier and beam foundation. 

It's going to take a lot of cleaning, plus the windows and such that you mentioned. 

The baseboard heaters are probably in need of cleaning.