I'm wondering if things have changed so much since I was doing this a quarter of a century ago? Most prints - and especially tiny ones as you describe - will not be wanted to 'exhibition' standard. People will bring you film in rolls and sheets for development and 'good' prints. Generally those would have been on RC paper. You need to print these in a few minutes, with minimal wastage.

Consider finding yourself a machine-processor for up to, say, 16" prints - few people who are not printing themselves will even know the difference between RC and fibre, and the processor will speed your dry-to-dry workflow enormously hence enabling you to offer a wider range of services. A machine-printer is most likely overkill these days, but if you have large orders (for example, over fifty straight prints per neg, if that still happens?) then it would save you time also. Unless you already have a name as a printing god you will be doing a lot more RC than fibre, simply because you have to charge for the extra time needed for washing, toning and finishing on the fibre paper.

Being able to cut mattes and offer a mounted print ready for a frame is an extra 'something' you could look at as part of your package. Dev+print to 10x8 or 8x8, with one 12x16 matted, clients choice. That sort of thing. This will set you apart from mail-order type places for example.

Look at the prices for simple but 'good' prints in well-known labs and you will find that they are surprisingly low. It is that sort of product which will be your bread-and-butter I expect.