First of all, welcome to the forum! I hope you find it to be a great resource for you and your store moving forward.
In terms of "buy now, pay later" options, your best bet would be to check out some apps currently available on our App Store. There is one called Charge Me Later which will allow customers to check out without paying, and you can then charge them at a later date. The app costs $8 a month and includes a 4-day free trial which can be used to test it out before you start paying. There is also an app called Partial.ly Payment Plans that allows for customers to pay in staggered payments, which might be of some interest to you.
I hope this recommendation is what you are looking for but please do let me know if you have any further questions!
Victor | Shopify Social Care