Get a small inverter and some batteries and your genny. If you buy a ready to run genny no problem, run the saw off it, charge batteries, use fan on inverter. Or build/buy a fan to run off 12V batteries and skip the inverter. The reason you want the fan running on batteries of course is you don't want to run a genny all night on those long hot nights just for a fan while you try to sleep. Otherwise you could just run the fan on the genny.
Now if your gonna build your own from a used engine and parts 
First get the engine setup and running good. Now take a 110VAC motor and mount it on the engine somehow and belt it to a pully with a ratio that will spin it about 10% (I think) above it's rated speed. You wire in a run capacitor across the wires (hopefully someone can tell you how to figure the value you need, I forgot). When the engine is running you will have a 110Vac genny to run your saw and stuff. Mount a GM Delco/remy Alternator (one wire type they are often called) to your engine. When you are running the genny to power your saw and stuff you are charging your batts for night time use also.
I beleave you want a motor rated for 2-3 times your expected use. Motors are hard to start this way, so if your running a 1/2hp saw you want 1-2hp motor for a genny, 1hp saw maybe 2-3HP motor. Turn off the loads before turning off the gennie.
Or you could take an easy way out and buy an inverter big enough to run everything and just charge batteries with alternators. I would use several if your using any big auto type diesels, more power than one alternator needs, run several and make use of the power.
I think for overall cheapness I would get an inverter that will run everything needed at one time, as many batteries as I could get, cheap diesel engine and alternators.
Reason for this is you won't want to be shutting down and starting the genny every few minutes while measuring boards, laying out cuts, etc.. (all the times the saw gets turned off short periods) so the genny would be running but doing no work or just a little if running the fan and lights. Far better use of feul to run it charging batteries a short time as needed then just run everything from an inverter. This way your getting lots of work for the feul burned, but when you shut down the saw and such your not wasting anything idling. Contractors don't care, they just tack it onto the bill you pay, but your paying the bill here so you probably do care if this will be used for any amount of time!
As for the batteries and inverter, I guess you will need them anyway later when you get the wind gennies flying
How many batteries do you need? That depends entirely how often you want to start the gennie to charge them really. Figure up all your amps/watts for everything your planning to run at once durring the day and how many hours. Say 8Hrs your going to be running 15 amps 120 AC, that's about 15X120=1800watts/12Vdc=150amps per hr from you batteries. Batteries last longer if not discharged to deeply, die quicker if run nearly dead very often. So how long do you want them to last and how many can you afford and how often do you want to run the gennie to charge them up?
More batteries are better for many reasons, but you could maybe get by with 600amphrs 12V. Not alot and I would charge every other hour durring heavy use. Most the time you would not be drawing the max anyway, would saws be running constant durring the day or off most of it, lots of cutting all at once then off again for awhile? Maybe start the saw cut a couple boards, shut it off, go hammer awhile, start saw cut more, etc...
A gennie would be running constant in most cases, batteries get to rest alot
