What's the Smart use of a HELOC?

[Armel Bayot]

Planning to refinance my primary residence and get a HELOC. I've just been saving money to fund my first rental property but looks like my primary residence has gained some good amount of equity . Read some articles that encourages to use it to slice down your Principal mortgage, some would use it to buy rental properties, and some just hates it. I'm leaning towards using part of it for REI and a portion to my principal. Would like to get your thoughts on using HELOC the smart way. Thanks guys!