Any time one can acquire a tool, they should do so. Even if it's some esoteric contraption for "one time" use. Borrowed anything is the start down a slippery slope. There are practical limitations such as funds, availibility, lead time on job. And more theoretical considerations such as suitability. Theoretical because there is always the fallback to a hacksaw or drill. I'm waxing philosophical here because such a question is very personal and difficult to answer remotely.
I have a Milwaukee line powered "Porta-Band" saw that was acquired for professional use. My splicing trailer had an onboard 5KW generator so battery powered tools held little advantage. The band saw still gets used where appropriate. There are other tools to choose from as the situation demands. From the hacksaws to cutoff wheels on a side grinder to a composition blade on a skil saw. Et cetera ad infinitum ad nauseim.
One big advantage to battery powered tools is that they can be converted to run on just about any power source. I have several older "cheapie" battery power tools that had marginal batteries from the git-go but the mechanical design was reasonably sound. I rigged a replacement plug that ran off my tractor battery for use in the deep bush. My interests at the time revolved around a small tractor. It could have easily been a quadra-trac, or a pick-up, an airplane, whatever. More modern tools of 18 volts are a little more difficult to arrange, but still doable. All that is necessary is a dead battery pack and a few feet of "zip" cord, and a couple alligator clips. Worst case, in the shop, is a battery charger. Old style without all those sensing gizmos, just a 13.2 volt DC power supply.
As I've aged (and broken down), many of those jerry rigged tools have been re-integrated into semi-permanent contraptions or passed along (given away) to someone younger with the need. Very little gets thrown away, there's always something that can be "made" from it, done with it.
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