If one didn't obtain any funding before being admitted into a Master's program, is it hard to find funding in the middle of the Master's? Are RAs and TAs strictly reserved of PhDs? Any funding other than RAs and TAs?
In many (I daresay most) departments, funding for Masters students is fairly hard to come by, especially for students in Masters-specific programs (rather than students who are in programs that are expected to roll into a PhD).
There are a number of reasons for this, ranging from Masters students being unlikely to produce much in an RA position before they move on to Masters students actively being used as an source of income for the department (this is especially common for professional-type Masters programs).
It may still be possible to find funding - I occasionally hire Masters students for short term projects etc. but it's definitely more difficult.