The problem with economical is it sacrifices power, durability, and often weight.
If you're just using it once a year to trim a couple trees, go buy a Poulan or Homelite for $100-200 and deal with the associated headaches. Be prepared for hard starting (especially after it sits a while), plug fouling, low power, etc. But for light work on a budget they're ok. Wal-Mart, etc.
If you're doing any sort of real cutting, beg borrow or steal the cash (250-500) for a Stihl, Echo, or Husquavarna. There is a world of difference, and you definitely get what you pay for. I'm partial to Stihl, but have used an Echo and a Husquavarna with no complaints. Lowes/HD etc have 'em reasonable but no real advice/support available, or support your local small business owner and buy from a farm/home store or landscape equipment store where they specialize in power equipment.