Taxes owed

I own an mlm that I just started.  I do local vendor shows. At every show they give me a sheet that I have to fill out to pay taxes.  I was told that I didn't have to pay the taxes because I pay taxes on the retail costs of the products when I purchase them to sell at a show.  I am just leary about this and don't want to owe a bunch of taxes at the end of the year.  I also am confused on whether I need to file and pay quarterly taxes on my earnings.  I have a full time job that takes taxes from my check and the mlm is just a side job.  On average I have purchased around $1000 a month and mark it up 40% .  So I guess that I will make around $5000 this year.  But I have a large amount of expenses that can be deducted, like show costs & shipping are the large amounts.  There were several shows where I lost money because of the large booth fee.  Help do I need to pay taxes on each show and do I need to be filing quarterly taxes?  If I have paid taxes on the retail amount of the items that I am selling.