Next spring I am going to be remodeling a barn on my property into a workshop. I initially got a line of credit with the credit union to cover the cost. It has a variable rate, but figured that made sense since interest rates are likely to go continue to go down in the near future and the plan is to pay off the entire cost (~90k) over a four-year time span. But now I am starting to wonder if it would actually be a better idea to just get a second mortgage with a fifteen year payback window and lock in lower monthly rate, and then still pay it off in four years.

I'm curious to get some opinions from any of you who might have done something similar, or for the couple of CBers who are in the financial business and know this stuff inside and out. Would one benefit me more than another one?

TIA