It all depends on the overall vehicle condition. 99k miles isn't crazy high on a vehicle with a factory service life of 250K miles.
My SRT has just about 90k miles on her and many here are in the 125k+ range.
Have it thoroughly checked out and then decide. If all is good, make your best deal and know that you have another 10 years of service life designed in.
Sure it will need some repairs and maintanence needs to be your first priority, but there isn't any reason you can't have it be a good solid ride for years to come.
2006 Inferno Red SRT-8
Option groups I, II, & III + Sunroof
Built Thursday February 23, 2006
Triple A Performance (AirFunnel, AirHog, Aces IV)
QuantumBlue Custom Blended Oil (Yeah, it's that good)
I will drive her until one of us dies! 1/4 mile: 13.388 firstname.lastname@example.org mph