I'm in the process of building a fermentation chamber, using an old mini fridge. If you don't want to build something, or buy a big freezer, then there are some other tricks to keep your fermentation temperature down, such as fermenting in a bath tub in a few inches of water while draping towels over the fermenter.
Even though I'm new to this, for my second batch I used a rubbermaid container that the carboy fit in. Filled to about 1/3 carboy height with water. When temps got to 70-72, threw a cup of ice in the water and kept it at 68. House temp is about 78-80. Can tell the beer will be better than my first batch, (no water bath, ferm temp about 76.) Fermentation was much slower and steady and the airlock gases smell much better. Would def recommend this for a cheap, easy fix.