Yes, you can enter the mower that you purchased to mow your rental property lawns. You can claim the amount that you paid for the mower. Enter the mower as an asset and you will have the option of choosing to expense it if it is under $2,500.
To enter assets from a rental property:
https://ttlc.intuit.com/replies/3288530
What can I expense or depreciate with the new business safe harbor election?
https://ttlc.intuit.com/replies/4682171