While candidates must demonstrate an income that they receive "without working", they may work at the management of their investments (including property investments) in the UK. The holding of non-executive directorships may also be possible.
Independent Means visa applications, should be made at the British Embassy/Consulate/High Commission in the candidate's country of nationality/usual residence. Successful applications usually result in the issue of a four year visa. Once a candidate has spent four years in the UK, as long as they still have the requisite income, the Home Office will normally grant indefinite leave to remain.
Independent Means visa applications usually take a few months for the Home Office Immigration Directorate to process.