Just some thoughts on tools I use all the time to make that extra couple bucks of an item. Feel free to add your tools/ideas
Pressure Washer
The go to tool whenever I decide to resell just about anything, It's amazing how much money this simple tool has made me.
Paint Gun/ Palm Sander
A coat of paint or stain on the right item will make you easy $$$
Buffing Wheel
Always check out the item first!!! if patina is not wanted then shine away, the shinier the better.$$$
Welder
I just have a little buzz box (arc welder) but it lets me fix so many items that just need a simple small weld to make them usable again. Making them worth more $$$
Books
I have many repair books. learning how to fix a common problem in items will bring in the dollars.
Although fixing up an item usually brings in good money, it's not fail proof. Just watch the time and resources being put into a project. Know when to call it before your too deep. Worst case scenario it ends up in the scrap pile and you come out a little bit wiser.
Bookmarks