Wire the garage for an alarm system. Check building codes for rules or insurance breaks on sprinkler systems. How large a driveway or concrete pad in front or on the side? Insulated doors to help with the A/C? Internet drop or wi-fi? Phone line? Dedicated electrical sub-panel w/ 220v line?

What else are you going to store or need on the property that may call for an out-building: rider mower? Excess Christmas decorations? Sports stuff? Bikes/Motorcycles? Work truck? Boat/jet skis?

If there's "extra" space in your detached garage, stuff will find its way there. I'm assuming standard Texas construction: slab, no attic storage, normal-ish closets.