The basic idea is easy enough: a state offers residency rights to overseas buyers who invest a minimum sum in property. The threshold differs greatly between countries, and the authorities change it with limited notice.
One key point separates residence and citizenship. The permit allows you to live locally, generally with renewals, but citizenship usually demands far more time and additional conditions. Any offer of nationality in exchange for an apartment purchase is reason for caution.
Past the headline threshold, such permits come with extra obligations. Frequent requirements involve proof of no criminal record, health cover, proof of income and a minimum stay on local soil annually. Ignoring any of these can cost you the residency while you still own the home.
Tax status is a different question altogether. Holding a residence permit does not by itself make you liable for local income tax, but crossing the day-count threshold usually will. A number of states use a residence test based on days, and the implications reach foreign income.
A sensible approach is the same everywhere: buy property in ajaria pick a buy property in meribel you would want anyway, and let the permit be the second reason. Programmes get restructured sometimes at short notice, and a property chosen only for a permit becomes a poor asset once the rules change.