Take a look at the professional websites and you will see that you need to charge a lot of money for designs you have to make from scratch. 

Sometimes the details have to be toned down and you still have a complicated subject.  The last request I was given was for a personally owned motorcycle - I turned it down and then found out it was presented to a professional embroidery shop who quoted at least $1,000 and told them the same thing - all details could not be included.

You have to break the picture down into an image that can be embroidered, then it has to be digitized and more times that likely, tweaked to perfection.   This can be very time consuming.

You begin with an art program to turn the picture or sketch into a jpg or bmp format before digitizing.  Clip art is already in an art form.  However, not all is free and finding one that applies to what the customer wants is not easy.

You could also sketch the logo and then scan it using the digitizing program.  This is usually easier than using a photo.  Make sure all the lines connect or areas will not fill.  I think of it as filling a cup with water.  If there is a hole in the cup, it will not fill.

There are a lot of expensive software programs and I am not sure any are super easy to use.

You might look at the site for Universal Stitch Era to get an idea how complicated and expensive digitizing can be.

Bottom line as to how much time it will take depends on the complexity of the subject. 

When it comes to free-hand sketching I am all thumbs and give the task to my son who is a super talent with anything he touches.