Just purchased our second 6x10 single. Love the singles. All our properties are under 1/4 acre. We run each trailer with a 50" to 52" Z and a 36" walk behind or 21". You can see in my profile how we have them set-up. We run no more than 2 guys per truck.
I think it really depends on the kind of properties you will service, the services you will offer, the equipment you will use and the area.
In our case it makes no sense to have the extra maintenance cost with tandem axles. Some of the cul-de-sacs are so tight you'd be scrubbing off tires quickly .
A couple of years ago I went in and had them start on a custom tandem trailer with all the bells and whistles. I am so glad I cancelled it because I didn't need it I only wanted it.