How much $$$ do you need? Most retiring-to-Spain British builders are worth £1M now; that's $2M.
I actually looked at the Spanish airpark a few years back. They were selling plots from £100k and house building options from £100k, so £200k to get in.
But when one thinks hard about this.... why? If you love flying, what you really want is an airfield nearby, but not the noise of planes taxiing literally past your house.
An airpark would be ideal for a residential flying school and the Murcia one was set up to support that. Almost nobody will be really living in that area.
Otherwise, you buy a house for the usual reason: a reasonable house in a nice location (not in some barren part of Spain). The French air parks tend to meet that requirement. In the UK, getting planning would be very hard in any nice location. A helicopter parked in the grounds of a big house is the only way to do that.
In terms of frequent business travel, very few people have the travel profile that would fit fixed wing in Europe. Those that need to travel by air a lot use a helicopter. Europe has killed off GA utility, with a hard IR, lack of IAPs, lack of airfields, etc.