Well, I guess I know something about them since I have one
I've had mine for 3 years and would not trade it for any other LBC... it's in a class of its own. It is seriously the most fun to drive car I have ever been behind the wheel of. Pound for pound, it's the most powerful 4 cylinder LBC you could buy. Did I mention I love mine?
OK, let's see. 1974 is a good year, that will be a MkII which has most of the "Lotus trouble" worked out. 1972s and early 1973s had some issues relating to the untested Lotus engine, but they got them straightened out by the time the MkIIs came out. Problem spots are:
1. Find out when the timing belt was last changed. If it's been more than a few years or 12,000 miles, change it. It's a $30 investment and a couple hours of your time, and is really cheap insurance against the alternative of having it fail and being faced with a $3000 valve job (yes, it's an interference engine).
2. Look at the T fitting that splits the fuel hose from the tank to distribute to the two carbs. If it's plastic, replace it immediately with a metal on. Again, it's like a $3 part. The stock plastic tees fail rather easily, resulting in fuel leaking down onto the starter and distributor... two places you do NOT want to have fuel leaking. There were a lot of engine fires because of this part.
3. Rust. OK, all LBCs of the era suffer from it, but the Jensen-Healey has an even worse reputation than most. Look underneath the car at the floor pans, right behind the doors where the rear fender connects to the sill, and also the sills themselves. Due to some "interesting" ways of designing things, these spots rust very fast (mostly due to owners not keeping the weepholes cleaned out, which results in water just sitting in those crevices). The sill is a big concern because it's a major structural part of the car, and if it rusts badly there isn't much keeping the car from folding up. I would get down there with a magnet and whatever else you need to do to make sure that the metal is solid and not just "Bondo-ed" over.
Off the top of my head, those are the big things to look for. If it's really in as good of condition as you stated, it's a gem of a car and I wouldn't think twice before buying it. They are really easy to fix when things go wrong, and parts are not at all difficult to find (it sourced parts from several other British cars of the era, and I've never had trouble finding parts during my restoration).
Oh, by the way.... to really get the most out of the driving experience, keep this in mind: that 7000 RPM redline is not a warning, it's a goal

Seriously, the Lotus 907 needs to be revved way higher than you're probably used to. There isn't a lot of torque at the low end, but she screams above 5000 RPM.