Depends...
If this is a blued 5" Series 70 re-issue....RUN...don't walk the XDM over to this guy and go home happy! These are usually very nice shooters...old school cool and they will hold their value, as most see "Series 70" on a Colt 1911 and immediately think its better than a Series 80 gun. The appeal alone of a Series 70 Colt makes it definately worth 700 bucks.
If this is a standard blued Colt Govt. Model Series 80...I'd probably still do it, as you'd be VERY hard pressed to find one new or nearly new for 700 bucks. It will still hold its value and despite what others say, the Series 80 guns CAN have good triggers and they're generally made with less MIM parts than Kimbers, Springfields or most other 1911s in its class.
If this is one of the "M1991A1" blued Series 80 guns with the wood grips...maybe. You can SOMETIMES get these versions of the Colt 1911 for around 700 bucks new, but you'd really have to do some work. These are good shooters (I used to have one) but they usually fetch less on th used market because they do not say "Govt. Model" or "Gold Cup" on th slides. This line CAN be built into a very nice cutsom gun and make for a good base start.
Your call...but just about ANY Colt 1911 is never a bad buy and you can almost always get your money back out of them.
I'd probably do it...especially knowing the previous owner and knowing for sure its nearly new.
- brickboy240