Before I had the opportunity to work on any of this stuff I used to spend a lot of time planning how it would go. I spent several years looking for websites of other people who may have done something similar so that I could hopefully learn from their successes and failures. Since the point of all this is how to spend as little as possible, I thought I would go ahead and document my "investment" screw-ups. So if you are about to spend a bunch of money on tools... this is for you.
So I had some land, but would not have power for quite a while. With this in mind I decided to get a bunch of rechargeable tools. My general policy is to go ahead and spend extra to get tools that will last (within reason), so I bought mostly Dewalt 18 volt since they seem to be the top on the consumer line and generally had good reviews. My first mistake was buying them in pieces. I needed a reciprocating saw while I was clearing land so I got that. Then I discovered that the battery only lasts for a couple of minutes of run-time, so I got a couple more batteries. Then I needed a drill so I got that. In the last couple of days I needed a circular saw. Luckily my dad gave me an extra black and decker 18v... so at least I did not have to buy one of those. Buying these in pieces at the local Lowes was my first mistake. If you get them as a whole set you will pay a lot less. Also Amazon is about 30% cheaper.
Some tools work very well off batteries. You can accomplish a lot with a Dewalt 18 volt drill. Other stuff I have to conclude was not really meant to be cordless. I would say reciprocating saws and circular saws fall into this category. With a new fully charged battery I get about two minutes out of the reciprocating saw... which is not great, but may be worthwhile as you can cut a lot of limbs and small trees with two minutes of run time. The circular saw (Black and Decker) however is almost completely worthless. Basically on a full charge you can cut an untreated 2x10 about 6 times. I spent the last four days cutting steps out for a staircase to the trampoline. The reciprocating saw could have done it but it is hard to make a straight cut. I cut a few out with a hand saw but for some reason all my cuts ended up bending as I went. In the end it took four days to do a 20 minute job because I had to keep driving 15 miles to recharge a battery to make six more cuts.
Having now spent over $500 on rechargeable tools I can think of a few alternatives that may have been better. I would probably still get the cordless 18v drill. That works great. Instead of the reciprocating saw I would have just got a $20 axe or machete. After that there are a couple of good options:
1. Get a Generator: These can be found surprisingly cheap. http://www.harborfreight.com/ has a variety of sizes but a 2200 watt generator which should run almost all power tools is about $300. Then you can get the other tools you need used or at a pawn shop for almost nothing. Also when all the building is done, you never know when you might need a generator.
2. Get an Inverter: You can get a 2000 watt inverter for about $160 also from http://www.harborfreight.com/ which you then hook to your car battery and let your engine idle. Then use corded power tools from this. If you plan to go off the grid at some point you are going to need one of these eventually anyway.
To find the max size inverter or generator you will need multiply the amps used by your biggest tools by 120 and add about 10%. You will need at least that many watts. 2000 watts will run anything up to about 15 amps.
3. Get a bunch of old used rechargeable tools and "zap" the battery. Last week we threw away about a dozen 14.4 volt battery packs that would no longer hold a charge. Then a couple of days ago I find this: http://www.instructables.com/id/Revive-Nicad-Batteries-by-Zapping-with-a-Welder/ I have not tried it yet but apparently you can revive an old nicad battery to where it is almost as good as new by briefly running a bunch of high voltage power into it. The voltage needs to be DC and about twice what the battery capacity is. This can be done with a bank of car batteries in serial, or a welder (about 40ish volts), or a capacitor from a disposable camera. My brother has a battery that will soon be dead so I will let you know if it works. BTW: be careful if you do this as the battery could explode.
Other possibilities that you can find fairly easily with a google search include modifying an old battery so that you can hook the rechargeable tool with a cord to your car battery. Or making an adapter so that you can use cheaper batteries from other manufacturers on whichever brand you end up going with. Both these really only require a little cutting and soldering and broken parts to accomplish.
One other thing I should probably mention. If you are going to be ordering a bunch of stuff you might want to become an "Amazon Prime" member. Basically for $80/year you get free second day air shipping on everything that is "prime eligible" which is everything shipped by them and some of their associates, which is basically most stuff. I actually bought the $250 trampoline from them which weighed about 130lbs and they had to ship it free second day air. I am fairly sure shipping for that was more than the cost of the trampoline. Had I been feeling especially nasty I could have upgraded that to next day air for $3. For people in rural areas this can save a lot of time an money in the long run. Also now you get a bunch of free online videos with it... kind of like netflix.