If you are looking to purchase a sewing machine but are not sure you will really use it very much, you should consider purchasing a used sewing machine. If you find a machine that looks like a good deal to you, search sewing machine reviews on the internet and look up the particulars of your machine to make sure it seems like a good match for you.
Once you have determined that the brand of your machine has received good reviews in the past, you should try the machine out. Give it a test run by bringing some fabric with you. Be sure that the stitches seem even. Make sure the machine seems to be in good working order and that it is easy for you to use. Take a look inside the machine to see if the belts look like they are in good condition, and if it seems to have been kept clean (i.e.- it is not clogged with lint or dust).
Once you purchase the machine, you may even be able to take it to a place that sells new machines to have them check it out for you. By reading cheap sewing machine reviews online ahead of time you will know if you have found a reliable brand.