to register trust for GST or not?

I’ll be using a discretionary trust with corporate trustee to invest in property.

Starting from nil. Expect to make both rental income and capital gain income as a result of purchase/reno/sale.

Don’t expect to exceed $50k rental income anytime in the near future. Does capital gain count toward the $50k amount above which an entity is required to register for GST?

Would like to canvass facts and opinions on whether or not is better to register the trust for GST.