It's really tempting to say that the IRS won't be able to do anything - you can't prove I spent/received this for type of activity.... but that's not how the IRS works. Once the IRS decides to audit, you are guilty until proven innocent. They will be elbow-deep into your figurative financial rectum, and you will (almost always) lose.
That's because they are very good at picking who to audit. If you can document all your deductions, and have all your sources of income declared, and stored it all together an audit consists of hitting print, handing the scanned copies to them, and waiting.
I think there is a valuable discussion to be had about the power of a federal agency that can so easily zero their sights on anyone they choose, especially when that same agency has admitted to targeting for political purposes in the past.