As far as a money pit, Actually once I redid everything on my TR4A years ago I drove it for years and spent very little money on it other than time and little fiddle stuff every now and then, I am hoping to have the same experience with my TR250, but realize the car is a little more complicated.
Lastly, if you keep your Triumph up or make it better than when you get it it will hold or increase in value.
That new Chevy/Ford/Honda etc. that you pay $300-400 a month on without thinking about it losses half of each payment or more to depreciation.