I'm currently looking to fill my rental again. I hopefully will be building an ADU in the next six month to a year. What am I required to tell incoming tenants?

Thanks in advance!

If they agree to pay $X,000/month in rent based in part on seeing a certain back yard when they come view it, and then you turn around and take away what may have been a critical factor in them deciding to be willing to pay $X,000/month, don't you kind of feel that this would be a bait-and-switch?

@Chris Mason thanks for the response. Yes - I guess I'm asking more seeking advice on how to do it without scaring people off. Perhaps I can offer a reduced rent during the time of construction? It's a decent size lot and they will still have a backyard. 

I'd just say the available space for the back yard use is like, 15-20  feet from the back door.

That the future plan is to improve the property and full access is needed to get to the rear of property and that area is reserved, so set the area aside you feel is needed for access and development, and just say here's your space, and measure it off.  They might not want to mow it if they can't use it.. 

If it's going to tie into existing plumbing, sewer, electrical some how off the main structure that may need to be disclosed but honestly if the neighbor next door put up a building and it blocked view they'd have no recourse, and would have to put up with noise.

I'd only adjust rent if your going to actually invade their living space for utility tie in's and that's if they ask. Otherwise you have right to enter with proper notice for service. 

Thank you @Deanna McCormick -- all very helpful. Yes the current back yard has proven to be too big for any one tenant to maintain anyways, so I like your idea of blocking it off so the boundaries are clear from the get go.