1. Your Plum has an internal limit just like your new Gold, you could call in and ask if you would be able to make $30k in charges in a month and they can test it for you and give you an idea where your internal limit is (keep in mind it will probably go up every month so if right now it's only $15k or something, it won't be long to get it up to where you need it if you want to put $30k+ a month through it)
2. I believe it will show on the statement (lets say the 1st)
10% Minimum due by the 30th
remainder balance due in 60 days if you choose the 10% min. payment
OR
entire balance due by the 10th for early pay
something along those lines you will see on your statement
