For the tax system, I think it will be best if you contact the appropriate body to help you calculate that in order to be on the right track. 
 
But for the aspect of selling your bitcoin to invest in real estate, if the price eventually reaches $120,000, that is your own choice to make, and if you have up to that amount of bitcoin, you can't hold them forever.
 
At some point, when your target price reaches it, you will definitely have to sell them off. Investing in real estate is also profitable, especially when you invest in a good area that won't be devalued or tempted by government development.