If you are reselling or mailing anything online, at some point it will be necessary to have a scale. Poshmark allows up to 5 lbs on their Priority mail label. If Poshmark is you r on platform you most likely can get away without a scale. If you sell bundles of jeans and or shoes, it is best to weight the package to ensure you are within the weight limit.
If your Poshmark package is over 5 lbs you will need to know the weight in order to upgrade your label.
If you are shipping on your own via Paypal, Pirateship or other methods, a scale is a must. Especially when listing your items to ensure you are charging the correct fees. First class mail goes by ounces, you want to get this number correct to avoid your buyer getting any additional fees upon delivery.
A food scale my work in the beginning until you are ready to upgrade. Below are the links to the scale I currently use. My first choice is ebay-to support my fellow ebay sellers.