Hey,
It really depends on the type of business your friend is running.
I personally believe that it's never a bad idea to have a blog for almost any small local business. You can come up with some brilliant idea for blog's usage if you think outside the box.
The purpose of local business blog? Greater awareness. Ability to connect content with your (I say "your" but I mean your friend) business social media - hence, more social following and interaction. Deeper and longer connection - not just one-time service that they get from your business but connecting with them afterwards. Continuous offer of value without pressure - they will be more willing to use your services again if you don't "push" them - just offering value at no-obligation (we all like that).
Here're some examples of how blogs can be used for local businesses and their benefits:
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Local restaurant.
Create a blog with free recipes. Something that might not be on your menu. Something very simple. "Meal in 10 minutes" or "Best Seattle Recipes" something simple like that. Can be local foods. Ask your chef.
You become an authority, people like your free (no-obligation) recipes and next time they think about where to go eat - your chances are much higher because of awareness (and with people that just found your blog online and this is their first visit). -
Local eye clinic
Create a blog about taking best care of your vision, tips for taking care of your contacts, tips to improve your vision with physical exercises,... Things you don't normally hear when you go to eye clinic for an eye exam.
This will build a lot of trust. They'll recommend you to their friends (who sit on the computer all day long and damage their vision, like I do haha) and they'll share it on social networks. Guess where they'll go for their next eye exam? -
Car repair shop A lot of people out there are DIY. Give them tips and guides for fixing things themselves (don't overdo it - they won't need you then), especially something that you don't specialize in. Or just have a blog with latest cool cars out there. Something of that sort. You put journals for them to read while they wait - why not have a blog with the same type of content OR even create a mobile version of your blog (it is easy with right resources) or mobile app because I lot of people prefer their smartphone to old-fashion magazine.
Just some examples. There's always something extra there that small business can "talk" about though blogging.
Hope this helps your friend! 
