Form Builder can connect with 4 different payment processors.
We recommend Stripe because they do not have a monthly fee or batch fees. Their non-profit rate is 2.2% plus $0.20 per transaction. The for profit rate is 2.9% plus $0.30 per transaction. When a form is connected with Stripe, the user does not leave the form. The user will not even know you are using Stripe. In addition, Stripe.com only requires the user's name and credit card info. No physical address is required. This few requirements make it very very easy for a user to make a quick donation or payment. The below options will all require the user's address.
To request the non-profit rate, you can follow the instructions here: https://support.stripe.com/questions/fee-discount-for-nonprofit-organizations
2a. Paypal Standard
Paypal standard (free) has a similar fee structure as Stripe.com (2.9% plus $0.30 per transaction). However, with Paypal Standard, the user will leave Form Builder to make payment at paypal.com. This can be a confusing experience for the user. You might consider using Paypal Standard if you already have it and want to begin using Form Builder quickly. However, overtime, you may want to consider using Stripe.com.
2b. Paypal Pro (monthly fee)
In order to use Paypal and have the user remain in Form Builder for payment, you need to upgrade to Paypal Pro, which is around $30/month. Because you can achieve the same result with Stripe.com for no monthly fee, we recommend Stripe.com. PaypalPro transaction fees are also 2.9% plus $0.30 per transaction.
3 & 4. Authorize.net and Braintree (monthly fee)
These solutions are similar to Paypal Pro in that they require a monthly fee. They may also have batch fees. We only recommend you use these gateways if you happen to already have them. Even then, we recommend that you take a look at Stripe.com. Braintree and Authorize.net have transaction fees of 2.9% plus $0.30 per transaction plus their monthly fees and possible batch fees.
Note: We do not share in the fees from any of the above processors. We simply allow you to easily connect any of them to Form Builder.