it will depend on how hard it is to get a wire from your breaker box to the garage. subfeed cable will run $1-2 a foot and the rest of the materials under $100 plus timer. you could have a 30 or 50 amp 220 outlet for a welder installed and buy/make a controller to take with you.
something like this
http://www.horticulturesource.com/ph-ec-tds-meters-test-kits-for-water-soil-timers-instruments-calibration-solutions-c35/timers-lighting-controllers-s118/ecoplus-30-amp-timer-box-comes-with-ecoplus-digital-timer-734105-p1969/?osCsid=5ac484c85887251cee2955f8b65e73b4
something like this
http://www.horticulturesource.com/ph-ec-tds-meters-test-kits-for-water-soil-timers-instruments-calibration-solutions-c35/timers-lighting-controllers-s118/ecoplus-30-amp-timer-box-comes-with-ecoplus-digital-timer-734105-p1969/?osCsid=5ac484c85887251cee2955f8b65e73b4