Most lenders prefer the guarantor to be a close relative, usually a parent, grandparent or sibling. Your guarantor does not need to make any cash payments. There is no money that changes hands with a guarantee. Some lenders will allow extended family members and even former spouses guarantors of their loan.
Choosing someone as a guarantor for you when you apply for a guarantor mortgage can be difficult because the options are quite limited. Banks usually only accept as a guarantor a close relative, and usually only an immediate family member. This means that it is likely that only one parent or sibling, often (but not always) a grandparent can be accepted. Distant cousins living abroad are unlikely to be an acceptable potential guarantor for most lenders.
Guarantors are generally limited to immediate family members. Normally, this would be a parent, but guarantors may include siblings and grandparents.