Do you need it? What’s the return, not what’s the cost.
Discussion
Hashrate heating and place for events and room for bigger family.
The ROI here seems pretty simple. What is the going rate per square foot of finished space in your neighborhood? + how much revenue will you generate and/or cost saves from hashrate heating per year - adjust this all by whatever your cost of money is (probably BTC is the hurdle rate). That is the ‘hard math’. The soft math is how much will you and your family enjoy the space?
Ping pong table is endless joy.