Am I running my numbers accurately?

[Matthew Maynard]

Hi BP,

As I'm looking at properties, I want to make sure I'm running my numbers accurately. I know a lot of things I see online won't be the best deals (not to say they aren't out there), but am I being a little bit too conservative in my estimates? Any and all feedback is welcome. Here's how I've been calculating my numbers:

Estimated rent: look at similar properties in my zip code listed for rent on realtor.com, etc. Easy enough.

Monthly taxes: Plug in the address on my counties' property appraiser website and it gives you an estimate of the new tax rate based on the sale price of the property.

Monthly insurance: I've heard 2% of total purchase price gives you a good estimate of how much insurance will cost per year. Any other guidelines for this category?

Maintenance costs: 15% of monthly rent, give or take based on the age of the property.

Vacancy: I've been accounting for 1 month/year of vacancy (so 0.083 times the monthly rent)

Property management: 10% of monthly rent

Exterior care: $80-100/month for lawn care (no snow removal in my region)

Utilities paid for by the tenant. And no HOA fee as most properties I've looked at that have an HOA fee aren't close to cashflowing.

Thanks in advance from a newbie!