Castle Newsletter #1: Things We’ve Learned, Straight to Your Inbox

Starting this month, we’re sending an email update to our supporters with one thing we’ve learned recently. September’s is below. Want to get these updates your inbox? Sign up right here.

Welcome to the first official Castle newsletter. (Yes, we did send one previous email to this list, but it wasn’t an official newsletter. You can tell because we didn’t start it with “welcome to the first official Castle newsletter.”)

We want to keep you, our earliest supporters and fans, up-to-date about what we’re working on. Hence, this newsletter. The format is simple: in each, we’ll share one thing we’ve learned in the past month. A startup is in many ways a system for controlled learning, and one of the ways we measure our progress is in how much we’ve learned.

This month: simplify, simplify, simplify. Or: how we got rid of tenant accounts.

When we first started designing Castle’s rent payment feature, we defaulted to an app that would require landlords and their tenants to create accounts. We did this without even really thinking about it—it was an assumption we didn’t even realize we were making. After all, to use a web service, you have to have an account, right?

Early wireframes for the tenant onboarding process.

But user accounts create friction. They force people to remember which email address they used to sign up, and to create and remember yet another password. And they add steps to a signup process that we want to keep as short as possible.

A few weeks into our design process, a landlord said to me, “You know, my tenants all communicate with me by texting. Why can’t you just do everything over text?”

It was a good question: why couldn’t we just do everything over text? And so, after a few frantic days in the lab, our new tenant onboarding process was born.

Now, when a tenant gets set up to use Castle, we give them a one-time link that allows them to connect their bank account. After that, they never need to interact with the Castle website again if they don’t want to. When rent is due, we simply text a reminder, and tenants can pay (and set up auto-pay) just by responding to the reminder. Their identity is tied to their phone number, so there’s no usernames or passwords to remember and no need to ever log in to anything.

Wireframes for the new tenant onboarding process. One screen, five fields (and two are pre-filled!)

Of course, for those tenants who want it, we’ll still provide an option to log in and view more details (like their payment history). But it won’t be required. As a tenant, you’ll be able to set up your rent payments once, and then never worry about them again.

I hope you’ve enjoyed this peek behind the scenes. As always, we’d love to hear from you, so please reach out anytime with questions, thoughts, comments, or haikus. You can contact the whole team at

Happy September!