We went into it to look after and care for disadvantaged children but did need sufficient income to support a larger house and our own children. One important point is the omission of the fact we spent most of the money on the kids with days trips, holidays and activities so didn't profit from the whole process but we did need to pay extra rent on a larger home and to keep our own kids fed and clothed. I'd also edited the post as it was more about our experience rather than the actual process.
We also considered local authority fostering after we left the agency but while we were all for it, it was our own kids that didn't want it to go forward as they felt we focussed on the foster kids too much. So we had to call it a day.
So yes we needed the money as we could not have done the job without it at the time. Fostering is not adoption. You are there to care and provide a loving family environment for (mainly) disadvantaged kids while social services find a more permanent, and probably cheaper solution for their long term care. You have to integrate with parents, doctors, health visitors, social workers etc.
Kids also move on and you then have to deal with never seeing them again, or hearing about them ever again....this is hard. I still dream about them occasionally and wonder what they are doing. After our first 9 month placement my wife couldn't function for a few days after they went to grandparents. Our last placement ended within 6 hours as they had identified a local authority carer and not told us. We picked them up from school said our goodbyes and they were gone.
Our placements lasted between 2 days and 3 years, between 10 days and 16 years old.
17 kids who were better off going back into the scary outside word than they were when they arrived. A job well done I think.
So yes a very rewarding career option if you have the patience and ability to share your family environment with other people's children. So much so my father in law still fosters well into his retirement, although that's a long term placement with no parent contact.