You can adopt or foster. You do not have to own your home, however the process involves you being able to prove an income enough to support a child if you are adopting. Fostering pays an allowance to support the child, however you continue to work with the agency or social services throughout the time the child is with you. For children under 5 it is usually expected that you would be at home fulltime.
For either option you would be assessed by the local authority or private agency. They will want to know about your entire background from childhood, what relationships you have had with family, partners and friends. They will want to know what experience you have with children. If you don't have much, then they will expect you to become involved in local groups such as after school clubs etc.
It is quite a lengthy process and some people find it all intrusive, but at the end of the day it is the child who is the most important person in the process. A typical adoption could take as long as 12-18 months for all the assessments and introductions to take place. It can also take a number of months (upto a year) before you can be assessed to be a foster carer.
You will need to attend courses in childcare, attachment and child development. Many children who are adopted experience some emotional difficulties later in life that can be really challenging to their adoptive parents, especially if they are older. Also children who are fostered have come from difficult/abusive/deprived backgrounds and have to deal with the emotional difficulties that this brings.
It is a long haul but many people have done it and reap the rewards that this brings to their lives. Look into what is available in your local area. The authorities and agencies are crying out for people who want to do this - but it is a long haul. Nothing in life is easy when it is so important to get it right though - so take heart from that if you decide