Be aware of what you are buying...
Owner reviews are usually valuable when the bike brand is not well known.
Ti frames can be good or not so good. It depends on the Ti...not all Ti tubes are the same. Some may be straight gauge tubing with adequate welds resulting in a 'dead' ride feel.
Carbon has been around for quite a long time and has been said a well cared for, never crashed, etc. frame can last a long time. But carbon frame technology and materials has improved year after year and were it me I'd go for a newer frame.
Also keeping in mind brake type...mech/disk...drivetrain...mech/electrical...etc.
Good luck and keep us informed.