I learned the hard way not to leave your equipment out of site and unsecured. I had to line trimmers stolen this way. Both were around $400 and in good condition, and one was only a few weeks old.
The other day I saw a solo operater leaving his backpack blower out on the gound by his truck while he was in the back yard. I don't care how nice you think the neighborhood is, I wouldn't risk it, since it only takes a minute to set stuff in the back yard out of sight (or lock the trailer).