Questions on ROI, New to investing

[Etrayu Fitzgerald]

Hello everyone! Complete newbie to real estate here.

I do own my own home (with a friend) but am new to investment.

A couple partners and I are looking into a property in our hometown. It's a duplex with tenants already living there. We used the basic "Four Square Method" video to determine costs vs income. And somehow came up with an ROI of almost 60%. I feel as though we miscalculated something.

One unit yields $400 in rent (1 bedroom) and the other yields $800 (3 bedroom).

Total Rent: $1,200

Duplex Price: $67,000

Down Payment: $3,350

Repair Estimate: $2,000

Closing Cost Estimate: $1,500

Total Investment = $6,850

We factored in:

Mortgage: $340

Mortgage insurance (we would have a low down payment): $40

Home owners insurance: $67

Property tax: $113

Vacancy savings: $60

CapEx: $60

Repairs: $60

Lawn/Snow: $120

There are no HOA dues.

Total costs: $860

So, our monthly cash flow should be $340.

Annual cash flow $4,080

Total Investment $6,850

ROI: 59.5%

I feel like this return is far too high.

Is there something obvious we're missing?

All advice is appreciated! Excited to be a part of things!