I was talking to one roofer and he wants 16K for a metal roof to put over shingles.

Exposed nails, ripped up shingles, etc. and can cause leaks. 

Now you need to place a ticket and go through the computerized system to choose why you are appealing the review.

-Durable New Roof: 30-year architectural shingles with wood repairs.

-Durable New Roof: 30-year architectural shingles with repairs to any damaged wood for lasting integrity.

In my area you have to strip the roof shingles at a minimum . 

This implies even if it has a new roof, I allocate the monthly cost for the next roof which in my market is about $50/month for detached asphalt shingle.  

Lets say my first potential flip is from 1900's, has 4 layers of roof shingles, outdated electrical, needs a new kitchen, plaster down/drywall up throughout the house, flooring, and a terrible, terrible foundation.

Oh there is no shingle damage, or there is.

Licensed with permits ~$3,250.HWT standard gas single family low efficiency without exhaust retrofit $900.Sand and stain hardwood floors, natural stain $3 per sf.Paint interior walls, ceiling trim and doors 3 tone paint scheme 2 coats $3.20 per sf (floor area cost includes paint)Click lock LVT flooring install overlay inclusive of prep and quarter round $4.50 per sf (materials and labor)Asphalt roof installation 3/1 - 800 sf bungalow with 2 layers of shingles - ~$7,900Standard porch cap replacement with 2 new precast concrete steps ~$2,500Used stove or refrigerator delivery and install $350New stove or refrigerator delivery and install $HD model specificUse this as a general guideline.