Many happy returns.
a roof over your head,- you've changed from 'we' to 'you'
These prices are fixed in advanced, which makes it impossible to bargain over them .- the language is OK, but can't we haggle over prices?
our expenditures- I'd use the singular or 'outgoings'
accept these prices as an entity- I see no need for 'as an entity'
- For Teachers