Help with New Roofing Solution -- Need a new roof pronto

Hey guys,

I bought a 1960s ranch on a basement.  It has an open vaulted ceiling and needs a new roof.  This is going to be a flip.  The present roof decking is an older material that is like press wood.  It is presently crumbling.  This material is no longer used for roofing.  My question is what decking material would you use?  Keep in mind that decking will be seen from inside the home due to the open vaulted ceiling.  I am looking for the lowest cost solution.  I know OSB decking is cheaper than ply, but it would require us to then do something inside the house because it would be an eye saw.  I was wondering if anyone knew of a solution where it would be a one shot deal.  Even though all of the decking isn't crumbling, as soon as we remove the ones that are, the new decking won't match.  So, we think that we will have to do a complete tear off.

Any suggestions would be greatly appreciated.  Oh, it's a lower end flip so cost is definitely a factor.