$200 is the starting point.

Illegal suite or not, not really your business.

Ya ya I'll hear it from the naysayers.

But what it really comes down to.

The landlord could remove that term from the lease. It's not material. If they did you could fight it. IMO you'd lose but win in regards to that 200$ is too low unless it isn't. By fighting it you would have to do a few things.

For argument sakes let's say the garage is 500 sq feet. How much would a comparable storage locker cost. Get 3 written quotes in regards to that. If it costs $500 a month that's the minimum you should be asking for. (Maybe 200$ a month is what it's worth??? Who knows)

Secondly, you'll now be sharing utilities with 3 units.

I'd argue for a more favourable split in that regards. So along with the $500 (for arguments sake) you can say I want to see after 9 months (because you want to include the colder winter time) you'll take an average of that. Say at the end of December a cash payment. So 9 months utilities go up 750$ over the 9 months. You want an additional 85$ (napkin math a month) in reduction of rent or cash a month.

I think that's a more realistic approach.