Not ungrateful

I don't want to appear ungrateful to Tim and Sarah, but it feels like control of my life has gone again a bit. Sarah was saying things like, "well we live in a house and an area we don't really like, we won't have any spare money either" but I've been there done that, and I don't think they realise that. I've brought up 4 kids on my own for years, I've already had to sacrifice and live in a house that was less than satisfactory when they were young. I've already had my struggle, and to be asked to sacrifice and struggle again in a tiny house with no storage and a big increase in rent.... I don't really want to do it. Tima dn Sarah say it's only a start for them and maybe in 2-3 years they will be able to buy a bigger house. But who knows what the housing market may be like in the future. And to be in that house for 20 years??? I don't think I can do it.
I am grateful in principle with what they want to do for me but not the way they're doing it.