Metal roofing advice

I am working on a fixer-upper house in the Memphis area with a couple of layers of leaky asphalt shingles over uneven boards, about 1500 sf. Because of the unevenness and questionable condition of the decking I plan to cover it with standing seam metal roofing panels.

What would be better - furring over the old roof, removing the old shingles and furring, applying directly to the old deck, or removing the decking as well? New decking is not an option, and I would really like to avoid having to deal with the old roofing. The main consideration is minimizing total cost and labor.

Thanks for any suggestions or sources of discount roofing panels!

I believe it's 6 in 12... looks to be about 30 degrees. Roofing is

Actually I would like a roof over my head, but thank you for your contribution.

Only a hack would do that.

Apply tot he old deck if it is sound. but be prepared to have to replace some on an old house.

Going to be a slum lord eh?

Then why do it the cheapest and least labor and have to do it again because it failed? Do it once, do it right, and it will truly be the cheapest over the years.