I would suggest that if your parents are happy with $200, then maybe give $225. This will cover what it costs them to have you there and some left over that they can put towards their retirement (if that's what they want to do with it). This also gives you a 'little extra' that you can save towards your next IP or to pay down loans. A win/win situation.
In addition to that, I would suggest that you do all your own washing, but you could help them out and do some of theirs as well, and you do a fair share of the cooking (I know I would appreciate that because I hate cooking & my lazy adult daughter lives with me and does absolutely nothing). Top that off with paying a share in the electricity, water & gas, and I would suggest that your parents would be as happy as pigs in mud, so long as you don't have too many personal disagreements when sharing the living arragements.
In addition to that, I would suggest that you do all your own washing, but you could help them out and do some of theirs as well, and you do a fair share of the cooking (I know I would appreciate that because I hate cooking & my lazy adult daughter lives with me and does absolutely nothing). Top that off with paying a share in the electricity, water & gas, and I would suggest that your parents would be as happy as pigs in mud, so long as you don't have too many personal disagreements when sharing the living arragements.