You can DIY, but based on all the things you have said, I think it is time you hire an attorney. 

No depreciation, no 1031s, no installment sales.

Use low maintenance materials as me tinned above.Have qualified installers who don't cut corners.Buy materials with long warranties as this usually signifies higher quality products.

I have just in the past month added a paragraph stating that the tenant must supply and use mouse traps, cockroach poison, foggers or other pest control products that are readily available in grocery stores and DIY supply stores.

In reality, 90% of the time you can probably do as good a job if you go the DIY route on the PM side as long as you invest time to learn how to do it right.

I'm not sure what area you are looking at but purchasing a lot here in colorado for example you'll have the costs of drilling a well, installing a septic system, running power to your lot, installing a driveway, etc, etc.

This gets complicated and is not a DIY project.And, depending on the specifics, various other limitations can come into play.

@Bjorn Ahlblad - i contacted the insurance company and ask how i could get my rates, one building was knob and tube wiring, I installed 3 x 200 amp SquareD panels my self.

They'll make sure all the windows work, and that the smoke alarms are installed correctly, that any stairway with more than 2 steps has a railing, etc. 

You can consider installing individual boilers for each block.