MasterVision has a complete contract module that handles both in-house and billing company contracts.
MasterVision's contracts can handle multiple students on one contract, family discounts, cash down payments, deferred payments, and previous contract balances. The contract screen instantly calculates monthly payment as you change interest rate or number of months. MasterVision prints the contract and can print the enrollment form for some billing companies.
MasterVision has the power & flexibility to handle both in house and billing company contracts at the same time. You can have some students with billing company contracts, other students bringing you cash, and other students with bank ACH transactions. This is explained more here.MasterVision can also do credit card payments through Stripe.com. This is included with no cost through MasterVision, but you do pay a Stripe.com fee of 2.9% + 30 cents. That's significantly cheaper than most billing companies. See this page for more info.