Probably about ~35-40 apartments in Barcelona. Going out to Spanish rural areas, you could probably buy ~4-6 abandoned villages with that, you'll get multiple houses, municipal buildings and whatever administrative stuff they had too.
You can definitely get a decent jet in that budget, there's a popular tech youtuber who recently bought one for considerably less. I'm pretty sure you could get like 6 houses in mountain view and still have money left over for a jet.
It's not just the acquisition costs, it's the employee payroll--two pilots, one flight attendant, engine overhauls every six months, other maintenance. See the Amalfi Jets video on costs.