The minimum age for taking out a residential mortgage of any mortgage product is 18. The minimum age for taking out buy to let mortgages is 21. Usually, the maximum age considered at the end of the mortgage term should be 70, or your state retirement age – whichever is sooner.
For joint mortgage applications, the eldest person of the two applicants would be used on application.
Mortgage offers are valid from the date the offer was made up to 6 months. There are mortgage offer extensions that may be granted in some cases upon lenders discretion.
Both residential and buy to let mortgages allow overpayments up to 10% of mortgage balance on an annual basis from the anniversary of completion. This will have a zero penalty on your mortgage.