WOW... So many dealing with the same issues. (single, working long hours, apartment living and potty training.) I really feel for you guys. It cant be easy trying to figure out what to do with you little once or how to go about getting them potty trained.
In your situations I would think that an xpen or confinement in a safe area of your homes behind a gate would be best. If pads are your only option than you will need to train them to go on the pad just as you would if you were commanding them to go potty out side.
Take them to the pad after every (drink, meal, nap, play time or long hour away from home.) Praise them and give a little treat like a Cheerio. Potty training for anyone regardless of your living and working situation is not easy. Be patient and be consistent...
Try this: Put several pads down in the designated area. Pups like to wonder and find just the right spot to go (usually once they smell there own scent.) A trick that I used for mine to get them to use the papers was to take a peace of the poo and place it on the papers. Leave it there for the pup to smell and to get use to their own scent. They soon figure out this is it... this must be the place. If you can stand to do this for a few weeks, replacing old poo with fresh poo every few day, it will work. Trust me.
I prefer Paper training over pads. You can read my paper training tips on my site and maybe try paper on top of the pads which will transfer the scent to the pads.
Training Tips - Dawn's Yorkies Ohio
I hope that all of you can find something that work for you and your pups. It can come down to trial and error before you find something that works best. But unless you want them to potty (use pads) inside the house 100% of the times you will want to start out door training with them as well.