most prop firms work for you, you pay the fees, commissions, to them.
some firms require a series 7 before you can trade. in order to get a series 7 you need to get sponsored to take the test. you just complete a u4, finger prints etc
spend sometime studying, it isnt a hard test but just very time consuming.
no, it prolly will not help you get a prop firm job. having up front capital is pretty much all you need to trade prop