@susier Thanks, he does use my laundry room and has his bins in my driveway and sometimes car so I'll work out the area. Thanks heaps for your response!
@onthepathtogod It's detached, shared laundry but it's a sleepout style studio. No bedroom just one big bed room, lounge kitchen and a bathroom. Thanks for clarifying, I will only subtract up to the value of his rent, as I can't raise his rent.
@susier Is the apportioned amount you can claim based on square foot? My grandad rents a 1bedroom unit on my property for super cheap ($100 per week including utilities and his own internet), and the square foot area of his property is over 1/3 of my property as he has the flat with a huge wheel...
@heatherb1993 I know it sucks but hopefully you can take some solace in the fact it will be worth more again one day. If you're planning on living in it for the next 20years I'm sure you'll see some great improvement in value.