In addition to sheer power, look for a model with a built-in thermostat so you can set it and forget it. This convenience feature is well worth it so you don’t have to stop what you’re doing mid-project to manually turn your heater on and off to maintain your desired temp. A good garage heater will mount to the wall or ceiling to save space and will come with a durable housing and full safety screen to keep dust and wood chips from reaching the heating elements and starting a fire.
Plan to invest in a set of bench chisels, both standard and low-angle block planes, a No. 4 or 4-1⁄2 smoothing plane, and a No. 6 jack or No. 7 jointer. Between them, these planes will true edges, flatten glue-ups that are wider than your thickness planer, and tame tricky grain that would tear out with a mechanized planer. They also do fine trimming better than any other tools.