Hi Jamie and welcome to the forum,
You may find that PayPal puts a hold on your account, it's done to many new accounts and lasts up to 28 days. During that period all the funds in that account are locked and you will have no access to them whatsoever.
I suggest you contact PayPal and discuss with them about you being a new account holder and seeing if you can given them your supplier's details for them to verify upfront. No guarantee, but you may find if they have this information up front it may well reduce your account's holding period.
What some do is sell one item only, pay for that out of their own pocket and then wait for the account to be reopened before trading any further, so that could also be an option to get you past that early hump in the road. Either way, I have always found PayPal much easier to work with when I approach them to head off any possible upcoming issue, rather then waiting for them to contact me, so I would recommend the same to other members.