I've got a Google Sheet that works well for me. It wasn't a quick process to get all the formulas working. Note, this worksheet is designed for analyzing the merits of selling a mortgage, not buying. YMMV.When sharing a Google Sheet URL on here previously however, I was warned that it allowed an uncovering of my Google identify.

https://docs.google.com/spreadsheets/d/1B_Tg0q_pokqSbSGNpynQHGosm7QUREf5Kg-KcbKxE5A/edit?usp=sharing

The above sheet is shared from a new, anonymous Google account. Please make a copy of it to enter your details.