A set of Cleco clamps go a long way to lining up rivet holes and keeping things square. Look on eBay for some great deals - everything to get started for about $50-75.
Grizzly is a little better on quality, but not the best. Import or domestic, it doesn't matter. Price and brand is more relevant to quality since the Chinese factories will meet the specified price point and make tradeoffs to meet schedule, demand, and specifications. Typical US importers want the lowest cost possible, and that's when quality lacks.
Swag Offroad has a shop press brake
kit you might want to check out (it may or may not meet your requirements - it does require welding). The Harbor Freight 20 ton shop press is about $160 on sale.
I check Craigslist nearly every day for miscellaneous metalworking tools. Press brakes and shears are a rare item now that many fabricators have long-ago switched to large multi-ton hydraulic systems.
Also, glad to see you are venturing into sheet metal!
