Welcome to Yorkie Talk.
These are the things I would consider in making your decision:
1) You already mentioned potty training. There are a number of people here who had an easy time with it and the dogs are 100% reliable, but I would say that the majority of people have problems.
2) Potential health care costs: possible liver shunts, broken legs, pancreatitis. Each of these can cost a $1,500 to $3,000 or more. Cost of routine vet care is substantial. Small dogs also tend to need more dental care.
3) What are your living arrangements -- house or apartment -- and how will things work with a large German Shepherd and a small Yorkie? Training that combination of dogs is not for everyone. It's beyond my capabilities and comfort level.
4) While Yorkies can be cuddle bugs, most need lots of exercise and activity. Will this fit into your schedule?
5) Do you like to travel and/or bring Brandy along? Traveling with 2 dogs is much more work than 1. Same with making arrangements for care if you leave them at home.
Wishing you the best in making your decision.