I'm trying to start a small business and I need to know how customers can pay me from across the country?

It started out small, with people I knew but soon word got out and people are asking for my product from other states. I can send it through UPS or FedEx but I haven't figured out how they will pay me. I don't want to use my bank account, just in case. What options do I have? Thanks in advance.
How do I use Pay Pal?

Get a paypal account.
All you need to do is use your email address and credit card and open the account and after you get the account you can put in your bank information

Then sse a free invoicing software such as www.handdy.com and send the invoices
Get the money electronically deposited to your bank account.
It is not hard