Preconditions for applying for a spouse visa:
You must intend to live together permanently with your spouse in order to obtain a spouse visa.
You must possess sufficient funds to pay you and your spouse's living expenses and those of any dependants without claiming public funds. Accommodation for the couple, and any dependents, must be suitable and available.
Spouses seeking to come to the UK on the basis of marriage to a UK national or permanent resident should apply for entry clearance before entering the UK.
If you have a visa valid for six months or less in the UK you cannot change the status to a spouse visa.
Children of the marriage who are under 18 years old are only allowed as dependents and can apply at the same time as the main applicant.
Spouses of UK citizens or permanent residents (mainly those with indefinite leave to remain) may come to the UK under the Family of a Settled Person Visa category, and also would be able to work as soon as a visa is granted. If you fall into this category, you can apply for an initial period of two and a half years as the spouse of a British citizen or Permanent Resident. You can also apply for an extension of two and a half years at the end of this period.
If a person has lived five years in the UK on a spouse visa and has passed the Life in the UK test, then the person is eligible for indefinite leave to remain in the UK otherwise called Permanent Residency.