I went to the Zoning Board to ask for an additional two units and got shot down, getting ready to go back to ask for just 1 extra unit.

Not only is that an occupancy violation but specifically marketing your property as student housing violates fair housing.I wish landlords followed the law, because putting the extra occupants in the property crowds parking on the streets and overwhelms them with traffic.

Every persons tax situation is different, but is there some kind of rule of thumb to determine when the extra cost of CPAs are outweighed by the savings of a larger tax return?

Cut all extras you don't need to survive. 

From what they have told me, they enjoyed the extra monthly rent to help pay the mortgage payment.

There is an income cusp you want to cross before the LLC may be worth the extra cost according to my CPA.

I looked at house hacking, but ultimately decided not to because I would still be coming out of pocket every month to cover expenses, or I'd have to live in a worse neighborhood which I didn't want.Instead I rent a place that is nice, but is below my means, and I invest all my extra capital into stock market and our own deals.

We agreed to keep the tenant for extra income, however at 28 and 26 years old, we found as ourselves as landlords, as well as first time homeowners.

Since it was recommended I wanted to find out of what value would this really be - extra cost I can use elsewhere.

Plus at my brokerage it costs and extra $125 per month not including any subscriptions to loopnet, coinstar, etc.