I am a foster mum to a 4 yr old lad with learning disabilities, and I also foster other children on a 'respite' basis, looking after them at weekends or anytime really that is convenient, to give their parents a break.
My two children were aged 4 and 5 when I started fostering and have always been loving to the children and look forward to them coming to stay.
Of course there are fights and arguments but no more than there would be if they were 'natural' younger brothers or sisters.
I thoroughly enjoy fostering, and the payment that I recieve for doing it enables me to stay at home instead of having to go out to work.
I hope that you go for it!