Do you mean a property in Regalia or in the factions/survival worlds? Reason being: The only properties with straight up pay are the noble estates. How you obtain those is by having a noble roleplay family, note that you can have a family with just yourself. After that it's just a matter of being active with said family and providing good roleplay and progression.
Here's the relevant thread for those:
https://forums.massivecraft.com/threads/noble-country-estate-reservation.47423/#post-620644
Other than that I am afraid there is no other way to obtain a mansion for a single paid price and even then, you need to do a lot to ensure that you keep your estate through the noble program.
Best of luck to you though, maybe you'll find another solution to your problem.