You can have a total equivalent Upkeep total of +4, for two or more labs. One is presumed to be your personal lab and another your classroom. You'll be provided a silver stipend and a vis salary every semester you teach. I haven't worked out the exact amount of the silver stipend, as of yet.
So, if you create a lab with BPs and the Upkeep total is +4, your teaching lab will be limited to an Upkeep of +0, or perhaps part of the stipend you're willing to forgo. I haven't established vis salaries, yet, but I have a pretty good idea of what I'm going to set it to be. Vis can also be converted to silver, should it become necessary. Keep in mind, based on the logarithmic (is that right?) progression of the upkeep cost, you can maintain a +3 lab and a +2 lab for Upkeep purposes and it is under the +4 Upkeep cost.
