I Built a Tool That Watches My Rent Spreadsheet (Here's What Changed)

I never planned to build a software product. I'm a landlord. I manage 12 rental units in Colorado. My tech stack was a Google Sheet and a prayer.

But one $1,400 mistake changed everything.

Before: The Google Sheet Life

For 3 years, I tracked every penny of rent in Google Sheets. One spreadsheet per year. Monthly tabs. Columns for unit, tenant, amount, due date, date paid.

It worked beautifully. Simple, flexible, free. I could see exactly who paid and who didn't. My formulas highlighted overdue payments in red. My summary row showed total collected vs. total outstanding.

There was just one problem. The sheet only worked when I opened it.

And I'm not a full-time landlord. I have a day job. I have a life. Some weeks I checked the sheet every morning at 7am. Other weeks, life happened and I'd go 5 or 6 days without looking.

Most months, that was fine. Most tenants pay on time. The 1st rolls around and 10 out of 12 payments show up like clockwork.

But the month it wasn't fine, it really wasn't fine.

The Breaking Point

September 2023. I was slammed at work. Didn't check my sheet for 11 days. When I finally opened it, Unit 4A was $1,400 overdue.

The tenant, Marcus, had assumed the silence meant flexibility. He'd had a car repair and spent the rent money. By the time I caught it, the cash was gone. We ended up on a 4-month payment plan.

I wrote the whole story in The $1,400 Mistake. The short version: it cost me about $1,800 in real terms when you factor in the late fee I didn't charge, the time spent chasing payment, and 4 months of stress.

That night, sitting on my couch staring at the red row in my spreadsheet, I had a thought that wouldn't leave me alone.

What if the spreadsheet could tell me when something was wrong? What if I didn't have to open it?

The Idea

The concept was dead simple. Connect to my Google Sheet. Check it every day. If rent is overdue and the Date Paid column is blank, send me a text.

That's it. I didn't need a property management platform. I didn't want to migrate my data. I didn't need a dashboard or a tenant portal or automated rent collection.

I just needed my spreadsheet to watch itself.

Building It

I'm not a professional developer, but I can write code well enough to be dangerous. I started with the Google Sheets API. It lets you read spreadsheet data programmatically.

The first version was a script running on a $5/month server. It connected to my sheet at 9am every day, pulled the current month's data, checked for blank Date Paid cells past the grace period, and sent me a text through Twilio.

It took about 2 weeks of nights and weekends to get it working. Most of that time was spent on edge cases. What about tenants who pay on the 15th instead of the 1st? What about partial payments? What if someone marks it "paid" but types the date wrong?

The first text I got was October 1st, 2023. "Unit 9C: $950 overdue. 0 days past grace period." I checked, and sure enough, Unit 9C hadn't paid yet. I texted the tenant. She paid the next day. She'd just forgotten.

That single text saved me from another potential multi-day delay. It felt like a superpower.

What Changed

The difference was immediate and dramatic.

I stopped checking my spreadsheet every day. This was the biggest change. For 2 years I'd opened that sheet every morning like a ritual. Now I only opened it when RentGuard pinged me. Most days, silence. Silence meant everyone paid. (I wrote about breaking that daily habit here.)

I caught late payments on day 1. Before, I might not notice for 3, 5, or 11 days. Now I knew the moment the grace period expired. Early intervention is everything. A "hey, rent is a day late" text gets a way better response than a "hey, rent is 10 days late" text.

My tenants were actually happier. This surprised me. When I texted consistently on day 1, tenants knew what to expect. No more confusion about whether I'd noticed. No more wondering if maybe they had an extension. Consistent communication builds trust.

My stress dropped by about 90%. I don't think about rent collection anymore. It's not on my mental to-do list. If something needs attention, my phone buzzes. If it doesn't buzz, everything's fine.

For context, I was spending 15 minutes every morning on spreadsheet checks. That's over 90 hours a year. Now I spend maybe 2 hours a month. Only when there's an actual issue to deal with.

Opening It Up

For about 6 months, this was just my personal tool. A janky script that only I used.

Then I mentioned it to another landlord at a local real estate meetup. He managed 8 units. Also used Google Sheets. Also missed late payments sometimes. His exact words were: "I'd pay for that."

So I cleaned it up. Built a simple website. Added a way for other people to connect their own Google Sheets. Added email alerts alongside the texts. Made the setup process take 5 minutes instead of 2 weeks of coding.

That became descoshop.com.

It's $15/month. No setup fee. No credit card. Free forever. Connect your sheet, map your columns, set your grace period, done.

What It Doesn't Do

I want to be honest about what RentGuard is and isn't.

It doesn't replace your spreadsheet. It doesn't collect rent. It doesn't handle maintenance or leases or accounting. It doesn't have a tenant portal.

All it does is watch your rent spreadsheet and alert you when something is overdue. That's the one thing. And it does that one thing really well.

If you need a full property management platform, go look at Buildium or AppFolio. They're great. They're also $50-100+/month and require migrating all your data.

RentGuard is for landlords like me. The ones who like their spreadsheet. Who don't want to migrate. Who just need that one gap filled: the spreadsheet can't alert you on its own.

Why I'm Sharing This

I know a founder story can feel self-serving. "I built a thing, please buy it." I get it.

But I'm sharing this because I know there are other landlords out there doing exactly what I was doing. Checking a spreadsheet every morning. Missing payments sometimes. Feeling that low-grade anxiety about whether everyone paid.

You don't have to build your own tool. That's why I built one and opened it up. Five minutes of setup and you never miss a late payment again.

The spreadsheet is great. I still use mine every day. It just watches itself now.