research licensing requirements for online payment system

Job ID: 32280855

Budget: $30 – $250 USD

proposed online payment system will take payments from side A to a transaction and either release them to side B or return all or part of them to side B after the allotted time has passed

i want to know what are the banking options for doing this nationally and internationally - is there an international banking system that would readily facilitate this or does it need to be licensed in each regime individually
would working with something like paypall be appropriate for this ?
what would be the requirements for various sizes of transaction - say :
a. up to $1,000
b. $1,000 to $5,000
c. $5,000 to $10,000
d upwards of $10,0000

are there special licensing / legal requirements for any this -

for example in a system such as this freelance is there a need for special banking requirements such as escro arrangements