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 with their Priority mail label. If Poshmark is the only platform you use, most likely can get away without a scale. If you sell bundles of jeans and or shoes, it is best to weigh the package to ensure you are within the weight limit.
If your Poshmark package is over 5 lbs you will need to know the escat weight in order to upgrade your label within the app. Poshmark allows up to 10lbs and the difference will be taken from your earnings.
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. Since First class mail goes by ounces, you want to get this number correct to avoid your buyer getting any additional fees upon delivery.
Any food scale will work in the beginning until you are ready to upgrade. Below is the link to the scale I currently use.