The houses are pretty much free, but come with severe problems.
#1 - There is serious consideration to bulldoze them to protect property price decline & crime spreading like a firestorm to the next street and so on.
#2 - Most require demolition, the unkindly but correctly called working class houses deteriorate very quickly in detroit and many were not in great condition before the crash.
#3 - Crime, insurance, mortgage are all issues.
A colleague was a Realtor for NatWest in the late 1980s, commercial property, and the only solution is a) run not buy and b) bulldoze a good section of Detroit. He put the reason, quite simply as #4.
#4 - There is a declining business base in Detroit, so the natural rising tide lifts all boats in the property market does not apply. The supply overhang will out last the ability of many neighbourhoods to remain standing. Detroit is a declining city, the demographic projection, socio-economic group projections, and migration is all wrong to consider it as an investment.
The problem with suburbs is when the economic clock turns, the market actually may not come back - which also works against their construction methods. UK has a high population density so this "post WWII dereliction apocolypse" is less likely.
Contrast with the peak prices for a shack in the Bay Area at the peak of the bubble, it needed USA Jumbo Mortgages to buy the door never mind the place.
Future immigration in the UK from EU is holding up prices, but now worrying the gov't is the transient nature of critical skills - amusingly the now much hyped "UK is nearly as cheap as China once you factor in transport" is not true. From duty on components driving manufacturers out of the UK (ridiculous) to basic salary vs living costs they are likely to rapidly ramp educational standards to try to re-establish pay levels. Competing on graduate numbers with China was a disaster, when China was added to the educational standards Shanghai came out #1 and THAT has woken up the West to educational debt being a millstone (people choose safe vs risk and it kills the moderate entrepreneurs, hence the polycrap UK, university left UK comments).
Detroit needs a few bulldozers or it could become a spreading cancer, it is the best way of driving other people AND business out. Business Capital Investment in EU & USA is absolutely chronic - we have a lost decade and this sort of stuff will not help.