I quit my software engineer job last June.

I know Quickbooks exists, but I wanted to make a tailored solution for their needs rather than just purchase some software for them to use.

Are there any actually good property management and accounting software for Canadian landlords?

The software I use to keep track of income/expense for this property has a category for renovations under capital expense.

Regarding background checks you can use many different apps or software, I personally like Hemlane for tenant advertising and screening.

Software is a common question on BiggerPockets.

For properties under $50,000 where HUD offers a flat $1250 commission to each agent the percentages are skewed but the number is somewhere in the minus $2500 + 5 to 6% as the minimum acceptable although occasionally a computer glitch(I assume the software was not set up for a flat fee commission) the counter will come back at minus $2500. 

If so, what is your favorite software to use?

depending on use case , one software migth take you there in 3 steps and another one in 5 steps ..

Software is a common question on BiggerPockets.