Actual, I have been hunting for my first armor piece for a few months and like you was wondering whether to go wheeled or tracked. I am leaning toward wheeled for several reasons: 1) as Austringer said, tracked usage is more limited, since you can't really use it on streets. There is some tracked armor (Saurer 4K and Stormer or CVRT family) that has rubber pads, but one guy that has it here says the rubber wears out fast and on his machine (Scorpion), it's imbedded into tracks, so once rubber is gone, you need NEW tracks. 2) if you buy tracked armor, you will need a truck and trailer to haul it around, increasing your $$ and maintenance and not helping things like storage and annoyed neighbors/unhappy wife, etc. 3) Tracked armor requires more maintenance, so it costs more to own/run. Also eats more fuel. Of course there is nothing like the sound of creaking tracks and shuddering machinery that makes you feel like you are invincible. So far, for me I've only experienced it by cranking up the volume on a good movie!
As far as Mortar Investments, I tried contacting them and others in Eastern Europe and wasn't really happy with their responsiveness. Yes, I got a few replies, but they weren't really offering me anything specific and I was not very comfortable at the prospect of sending money and praying for a long time until something got delivered.
I am now leaning toward a Ferret, which is a small armored vehicle produced in Britain in late 50's and 60's. There were around 4,000 made, so they are still plentiful and not expensive. For your budget, you can get one fully overhauled. I am working with someone in UK that has overhauled a couple of them and plan to have him buy a beater and totally refurbish it for me. You can look at youtube, there are tons of videos on Ferrets, which I am told make perfect 1st piece armor.
The Russian BMP's (early BTR's prior to BTR 80) have 2 engines, so maintenance is an complex undertaking. Also some of them are oversize. Not sure the rules in Norway, but here in US, you cannot drive anything wider than 8 feet 6 inches and I think the big boys are over 9 feet wide. You can look at BRDM-2, a Soviet armored wheeled vehicle, has 2 axles and also belly wheels. I ultimately ruled it out b/c I didn't think I could find someone trustworthy to overhaul it there and I don't have the skill or time to do it myself. But they are very plentiful and inexpensive, so if you want to work on them yourself, it might be a good fit.