Jan,
I always try to charge the client the least amount of time for the services I provide. I would say that on
average it takes me about 20 minutes to keyword a photo in the search section of the photo site, look through the photos, select, purchase, download, upload, resize, format and insert a photo into a blog post.
That's an average. There have been times it has taken me 10 minutes and other times, I've been so stumped for a photo, having to check several sites...even Wikipedia public domain photos that I've used 30 minutes or more.
There are times I take my own photos too for a blog post if I couldn't find a good photo online.
I offer blogging packages which includes time for photo searching and posting. But most of my clients for whom I blog buy retainer packages from me in which case I keep track of my time used.
Please don't let the photo-search hold you back from blogging. You can blog and then go back and insert the photo later. It is to your benefit to get those blog posts up especially if you plan to offer blogging as a service, you will want to attract people to your sites where they can see the good work you do. So I highly recommend that you blog and worry about the photos later.
Another tip: I buy most of my photos from iStockphoto although there are many other good and free photo sites. One benefit I like from iStock is that they give away one free photo, audio, video, audio and vector selection per month. I have signed onto their newsletter. Every month they send me a newsletter which is a reminder to go on their site and download the free photos. When I write a blog post, I will search my free library for photos and often use those for my blog posts. That saves me a lot of time.
You can also take photos with a camera and keep them on file until you need them. Take pictures in groups and then file them in groups such as 'nature', 'flowers', 'sunsets', etc., and then use those in your posts when you need them.
Finally, if you are really stuck for a photo you can create your own image using a site such as
FotoFlexer.com. Sometimes images don't have to images. They can be text-based images with slogans, sayings and single images.
Here's a link to several free photo sites that might be of use to you.
http://www.my-creativeteam.com/blog/...-for-bloggers/
Janine