I thought about doing this. You'd need to devise corporate prices/packages to make it work though and ensure that the company/premises has the right facilities for you to work in e.g. for massage you'd need a private room big enough for a bed and room to move around it.
You would probably need to offer your services on a day hire option, where the company hires you to treat staff as a corporate benefit to their employees. If you find the right company, they might allow you on site to treat employees on their breaks and the staff pay for the treatment themselves but I don't think a lot of businesses would be down for that on a regular basis (monthly for example).