The IRS has a whole pamphlet on travel and per diem and how much is allowable or not depending on location. Because it is easy to get into a this is income and that's not, I would read this pamphlet very closely.
The IRS link is
http://www.irs.gov/pub/irs-pdf/p1542.pdf.
I would enjoy traveling as a VA for a partner with the expectation that my travel expenses and per diem would be picked up and that I would receive a mutually agreed upon sum as income for the time I was working on the client's project.