I have heard that big dogs are easier to potty train than small dogs.
My first yorkie did take a few months longer than we expected to become potty trained, but she eventually got it and was a very good girl from then on. She earned the run of the house.
Because I am a flt att, my schedule changes all the time. I am home for different blocks of days all month long. I am married to a man who has a normal schedule. Our girl Molly would sleep a lot during the day when I was home, so I wouldln't feel too badly about working during the day. Especially because your two have each other.
We would go on our walks in the evenings most of the time, to accomodate my husband's schedule. That way our girl got her walk whether or not I was working. (We lost our girl in January
)
We will be getting a new yorkie in about a month. We thought of getting two, but I won't do it at the same time because I just don't think I can potty train two simultaneously without sending my husband over the edge.
I have also heard that it can be easier to train your second dog bcuz it will imitate the first dog. So I will hold off on getting my second until then.
Good Luck.