I'll chime.
Reliable? Depends. These 7s can be screwed together well and the car shakes itself apart. It's part of the bonding process and journey.
Price? With all the 7s that show up for sale, $25k is about right for a good 7, even a Crossflow. I think you could have your tucas three inches off the ground for half of what you're looking at. But, it's the whole package and this is your your chance to get it.
Investment? Nope. The next guy will always haggle you down. Wear and tear, damage, etc. You can't be looking at the resale. If you can't enjoy the 7 without worrying about the money hit later, buy a cheaper Caterham. They're all very similar. Just get a DeDion.
Maintenance? This is not reliable transportation. If a 7 is reliable, someone knows what they're doing. I would encourage you to "get into the car". Learn all you don't know so you aren't reliant on someone else. That may not be in your priorities. Doesn’t a aircraft pilot know his craft well? Absolutely, inside and out. Its a very simple car really. Knowing the workings is being pit crew and chief mechanic for your race car.
I'm not going to say you would do this, but here's a story.
I knew a software engineer type who found his dream 7 for sale. It was a used race beater with the typical mods. Well sorted. It was bought and shipped to him via a car currier. He asked me to come by and give him advice on how to operate the car (red flag!) I got there and he had the biggest grin, he was so proud of himself. He had connected the battery and driven the 7. I saw it coming. I opened the coolant cap, no coolant. Probably no oil either. The car had been prepared for shipping and fluids were drained. I got out of there quick and the blame game started between buyer and seller.
KNOW YOUR CAR.