Wanted to know if paypal allowed this functionality within one form or if I have to create two separate forms in order to obtain this functionality. Currently building a donation widget for a client per their request.
If there are any documentation regarding this within paypal a link would be greatly appreciated.
Cheers.
You can do that no problem. Just build your form with options for one-time or recurring payments, and then use the Express Checkout API to process the checkout accordingly.
If you're working with PHP you can take a look at my class library for PayPal, which will make the Express Checkout API calls very simple for you.
The calls you'd be utilizing are: