any advice on how to successfully invest in fire damage properties (pro's & the con's)
Find a good price and a good renovation contractor that deals with smell abatement. The more damage it is, the more beneficial it is for you to bring the price down.
The best way to deal with the smell in my experience is to get a paint sprayer and spray the structure with a shelac base primer.
Remove the drywall, have the ducts cleaned, remove the insulation, and figure the electrical is shot.
Any wood that has more than 1/8 inch of char should be replaced for structural reasons. If less sand it.
Make sure all the smoke smell is gone before you start doing any remodeling or you will have to rip up what you did.
Fire remodels cost a lot so be sure to have a nice cushion to work with on the profit.
I have eliminated smoke odor in about a dozen fires this way.