I'm applying for a MS at 4 different schools. I received a funded offer (TA position, tuition waiver) from one school who asked me to accept the offer by March 7. I am thankful for the offer, however I have more interest in another school that I applied to. My other 3 schools are in various stages of reviewing/deciding, from what They've told me. With today being March 2, should I accept the funded offer, and then wait to see what else is offered to me, knowing that under the Resolution I can submit a resignation of the funded offer? Is this a common occurrence?
You haven't said where you are applying to. While not a law, the offer you received would be in violation of the CGS resolution that offer should be until April 15th. Most universities in the US are signatories and follow this practice.
Regardless, there's no reason to tell them before March 7th considering that's the deadline they set.
Separately, depending on the sort of communication you've had with other schools, you could ask them if they will be able to tell you before March 7th to simplify your decision-making process.
The CGS resolution exists precisely so that people won't be stuck in this position (among first offers of funding).