Re: How to determine if old lap siding is salvegable
The fact that this is a rental has an impact if it were my project.
I actually have a similar situation I plan to tackle in two years or so, the rectangular tile w/ asbestos over wood lap circa 1900 or so. Tile was added at an unknown time, tarpaper placed over original siding. Every time I cut a hole in my walls and look at the siding the back of the original looks good, but I have to accept that 90% of my siding may be rotten and have to live under that assumption until the asbestos is removed. I can only be pleasantly surprised if things are in good shape. 50 years of hidden surface means you have no idea what is under there and any assumptions will be defeated by Murphy's Law.
Regarding the asbestos tile, I will tell you what a contractor I know of told me I should never ever do, and you should never ever do this yourself if you catch where I am going.
Hire a few guys, be it the painters or just laborers, to do your demo starting the Friday afternoon before a holiday weekend. The demo likely will not take more than two days unless your place is huge, get it done fast, and arrange for disposal. Local code enforcement will likely not work past noon the Friday before a holiday. You will have some cleanup if you hired hurried labor, so have fun with all of the nails on the ground.
Again, you should not do that, it may skirt the limits of legality.
Personally I plan to do my own demo for everything but a small section that is above the original roofline as I feel I can tackle one wall a weekend. The tiles are actually inert and harmless unless broken and the asbestos fibers become airborne.
It's this old house, not this built after your dad was born house.