Many projects require the use of Hardwood, and often there is not enough of it around. South-West of your farm is a forest. In the top corner of the forest, past the big tree, there's an Old Log that requires a Steel Axe to break. Go past the log and you'll find yourself in a secluded area which contains multiple stumps that give around 2 Hardwood each. This area replenishes the stumps everyday so you'll never run out. This is a good method for those struggling to find Hardwood.
Hardwood sells for 22g.