i have made some small investments in course material s here and outside BP.  

Whether that's your GC or someone else, time is money and subs can't wait around for decisions to be made or materials to arrive. 

And folks who maintain jobs and are apartment material will of course keep paying rents (albeit with some concessions, perhaps). 

If they had already prepurchased some of the material needed for the repairs and things like smoke detectors, would they normally be able to use it on a different home or would they get upset over it?

I don't know how to price the materials.

Purchase price 147KListed for 299K, sold for 285 (went under contract for 290 but dropped it another 5K at buyer request after the appraisal just to get out of the deal)Home Depot credit card: 10K (appliances, fixtures and other things we picked out and purchased ourselves rather than having GC use typical builder grade stuff, also husband did some of the work himself so bought his own materials)Brought 40K of our own cash to the closing table, loan total when paid back was 185 (original loan 175 plus 10K in accrued interest, 12 month balloon loan so we did not have to make payments during the rehab, which helped a lot with cash flow, also loan had rehab costs folded in so for the most part we paid our guys out of the loan and not our own pockets)So (numbers are round): 285 sale price - 185 (loan payback) - 40 (cash we brought to closing) - 10 (Home Depot card) - 10 (closing costs) = 40K profitWork done: insulation and vinyl siding (this ate 18K of rehab budget but was unavoidable as cedar shakes were disintegrating), converted to natural gas heat (ducts already in place, changed out electric hot air blower to gas one and gas company ran the gas from the street for free), replaced AC compressor, new water heater, two new bathrooms, replacement windows, new appliances but left the wood cabinets b/c they were in perfect condition and I could not justify painting/replacing them, new kitchen backsplash, removed wall between kitchen and dining room, wood laminate flooring throughout except for new carpet in downstairs den, painted the deck/railings, new garage doors, one new slider, all solid wood interior panel doors, of course fresh paint and new light fixtures throughout.dining roomThere was moisture damage downstairs from bank not winterizing and pipes bursting...thanks, bank.Hauled out enormous old woodstove and broke up ugly old hearth and left good flue for someone to add new pellet or woodstove to if they want to, we figured not everyone wants a woodstove and this way the buyer can decide to add one back if desiredBathroom off downstairs den, chose a walk in shower for variety, hosing off dog or muddy children, disabled access, etc. 

They want a house with four walls, a functioning roof, and rough and finish materials that work.

The biggest issue is porous materials like wood.

They don't have an actual text book to read from but rather it is all interactive and they cover the material (supposedly) that would be in a text book.For those who have their licenses, how did you go about it?

Dewalt has a book that gets fairly in-depth for estimating materials needed.