Cannot afford to replace Subaru Impreza air filter yet, so can I just take it out & vacuum it and then put it back?

Walmart sells air filters for Subaru Impreza's for $6.  A cheap clean filter is better than an expensive dirty one.  Otherwise vacuuming isn't ideal since it doesn't get rid of the fine particles that get embedded within it, but it's certainly better than doing nothing at all since you can at least get rid of the large debris. 

- Here at Crawford you will only ever hear proven facts, and the information ... You get what you pay for in the automotive industry, so bargain shopping ..

Take it out and tap it to remove any loose dirt. If you can't see a light bulb through the air filter buy a new one. They likely don't cost more then $20.

Better be changing your oil and filter every 3,000 miles dude.

Fram filters are about the price of a meal at Mickey Ds.  If you do not have this cash, you are seriously hurting.  Vacuum the filter if you are really broke.

Seriously?  An air filter costs about the same as lunch at Denny's.  Don't be so fantastic.  

Do the best you can with what you got. It is better then nothing.

I wouldn't use a Vacuum

you could use an air hose or left blower and blow it out

Never used a vacuum before but have used the air hose and it worked pretty well.