Hard to say for sure without the property dimensions, but just looking at it in the pictures, I'd say $300 would be in the ballpark, but perhaps a bit on the low side, depending upon the trimming, edging, and blowing required. I do agree to look at as 3 separate properties. Add the 3 prices up, and maybe do a slight reduction because you staying in one spot and only having to invoice one owner.
Since this is through a friend, you might ask if he can find out what they have paid in the past. It doesn't mean that price will be correct, but it will give you a starting point, plus let you know what they have been comfortable paying in the past. In my experience, people with money, are often the tightest. I mowed a single family home for an attorney a couple of years ago, telling them I'd do it for $100 the first time, then give them a price for routine maintenance. After doing the property, I called and told them I'd have to have $125 per mowing, based on weekly service. His wife said they just couldn't afford that, and I told her that was the best I could do considering the size of the property and the difficulty involved in mowing it (on a hillside). Took me about a month to get that $100 check, too.
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