New Build - Basement a good or bad idea??

[subirg]

As per the thread title, is it a good or bad idea to plan to build a basement as part of a new build? We have already got planning permission for a new build. At the mo its about 4,000 sq ft, ground floor and first floor contemporary design. We don't want to add floors ('cos we like the design), but we are tempted to add a basement for things like gym, storage, man cave etc. Is it a good idea or not? I've heard lots of horror stories of basements costing loads to build and not returning the investment, but I've also heard that doesn't need to be the case. We are not building for profit - we are building to live in this house for a good few years (10+), but I still don't want to put money into something that won't pay back.