This subject seems to be one that many clients ask. Self-employed people mainly base their work place at home although work may take place at customer locations. This can be many trades & professions from plumbers, accountants, chiropractors, computer technicians etc. It also covers freelance musicians, actors and other performers.
As you visit customer sites, it would be reasonable to be able to charge to your business the cost of getting to the customer locations. But, there is a little bit of an issue if when you walk in after being at customer locations, your trading activity stops as you get home. If no work was done at home, it implies that home is not the true base of your business. You need to make sure that business happens in the home such as writing up proposals, quotations, invoices, research etc.