I can tell you from personal experience that a living donor kidney is much preferable to a cadaver kidney for the recipient. My husband went through extensive testing to ensure that he was healthy, well adjusted and comfortable with the donation. They give you lots of time to back out if you want to, right up to the donation day.
The procedure is laparoscopic and he was only in the hospital 2 days and didn't need any pain medication when he got home at all. The incision is low on the abdomen and can hardly be seen when healed. He has an active job and so had to wait 2 months to return to work, but felt fine after about 7-10 days. When the MD says it's OK and you are fully healed, you can return to work, play and sports without any restrictions.
The body can function perfectly well with one kidney and there are no indications that only having one will lead to complications or increased risk of disease later in life for a kidney donor who continues to practice moderation and healthy living habits. Regular check-ups continue after kidney donation, just like for anyone else.
He is not required to take any medications, that is for the recipient who needs to prevent rejection - so I will be on immunosuppressive meds the rest of my life with this kidney, but it's a small price to pay for the freedom and good health I now enjoy.
My husband has since shed some extra pounds, works out, is feeling great and looks forward to years of health and activity - now with a healthy wife at his side. He is my HERO!
Be sure you are ready to take time off for the recovery and follow the transplant Docs recommendations after surgery. You will certainly be someone's HERO if you do this wonderful thing for them.