I keep forgetting about the sub-forums! I'm not surprised to see that truck is still wafting about on the market. It looks nice but really isn't a bargain for any kind of commercial operation - maybe fun as a hobby piece or plaything but not viable commercially.
Apart from the investment of money and work needed to get the equipment up to the kind of level that would be expected in a modern mobile of that size - bearing in mind that much smaller vehicles with far greater capabilities are now generally preferred and readily available - the running costs are high and it's a 20-something year old chassis cab which isn't going to get cheaper to maintain.
Also, parking (and even manoevering) something that size in most cities can get pretty expensive compared to something like a Transit or Sprinter sized panel van. If the venue doesn't have it's own dedicated parking, fees will be a multiple of parking a smaller vehicle and, in some locations, will require special parking arrangements and pre-arranged permits, or getting roads closed (been there!), rather than just parking in a normal parking space. And then there's the challenge at some venues of actually fitting the thing into the available space! Not so much of a problem at large concert halls or stadia but potentially really tricky at smaller club and pub type venues and city centre venues like theatres, clubs or churches. And as for those rural music festivals and classical gigs in country churches or stately homes, with narrow lanes, weight limited bridges, low overhanging trees, arches over gateways, etc., etc.!
The real nail in the coffin, though, is that with a vehicle that old, it's going to be nowhere near meeting modern emissions standards so driving it into major cities which have Low or Ultra Low Emmissions Zones is going to incur fees, which can run into hundreds of pounds or euros per day. And in some places, if your gig finishes late enough for you to be driving in the LEZ after midnight, you pay again. If you're paying Β£300/day to take your old truck into the LEZ, a couple of those payments can really eat into the profitability of the job, or price you out of the market if you pass the costs through to the client.
If I were looking for mobile these days (and having once had two trucks at my disposal (a 3500kg VW van conversion and a 14,000kg purpose built mobile) I do think about it sometimes), I'd be looking for something around 3500-5000kg (definitely no more than 7500kg!) with the ability to do surround monitoring and handle at least 3 MADI streams on a decent digital desk - preferably Lawo or Studer, or maybe Digico or Calrec - with double, or preferably triple head recording. All installed in a practical, comfortable, and aesthetically pleasant environment with some useful isolation and reasonable acoustics (and air-con!), based on the latest low emission specs or maybe even a hybrid or electric base vehicle.
Lets face it, if it's just a track capture job from MADI, an RME MADIFace XT and a decent laptop can hoover up three MADI streams and there'd be no great difficulty carrying two or three such systems in a rucksack! Add a little UPS for a few minutes backup for the RMEs, a MADI capable headphone amp, and a drum or two of multicore fibre and it's still not too bad for lugging around on the train in maybe a rolling case or two. OK, if you want to do a live surround mix or the kinds of things that a mobile can accommodate, or carry a load of mics, stands, cables, etc., etc., then a mobile is probably the way to go but a lot of the bread and butter tracking with a rough monitor mix type work no longer needs truck loads of fresh air and heavy gear.
A 20 year old truck with 20 year old gear really isn't going to be a fun option. One would probably make more money by installing a massive flat screen, a PlayStation, LF heavy surround sound system, some sofas and a stripper pole, bar and lighting rig to pick up the party group work. Or put a big door in the side, install some hot plates and fridges and go into the food truck game at festivals.