How long does it take an iguana to fully grow and how much does it cost to take care when its fully grown?

well ive had 2 iguanas but they died one of bone disase and not sure what the other one died from but it was about 3 or 4 yrs now i want another but not sure where to get a healthy one i want a baby and i know they sell them in alot of places but some of them dont look healthy at all but i was wondering from people who have or had fully iguanas to let me know what im in for i know they get really big but i just wnated to know if its hard to take of it when its fully grown and how much money an i looking at spendin while its in the prosses of growning.