If you are a new business or startup you are probably on a tight budget. You would love to lease that cool creative office space in downtown Austin however with the least expensive rental rates being $45 sf gross up to $65 gross that location is probably not going to work.
If you are looking for the cheapest office space in Austin you are more likely to find that in the Northeast and Southeast part of town.
Northeast or Southeast Austin may not be a desirable location for your business however at this time it's really the only areas of town where you will find rental rates ranging from $21 to $25 gross. That includes electric and janitorial.
Keep in mind that in most cases the cheapest office space is also going to be older Class C office buildings. These buildings are typically older (10-15 years or more) with few improvements and may not be maintained as well as other classes of buildings.
You could also consider renting flex office space which is typically found in semi-industrial areas in NE and SE Austin as well. The inside will still be built out as office however the buildings will be single story tilt wall buildings that look kind of industrial.