wanting to retire to Botswana (Gaborone)

Need information regards residency permit and permanent residency the rules regards both would be very helpful. I wish to buy a property with some land and stay in Botswana I am a full UK citizen born in Scotland. We have our own private income so do not want to work or start any business there. Hope somebody out there can help. Tried government web site but does not give any answers. Thanks in advance Best Regards Hugh & Jennifer