Also, you learn info such as where historic districts are etc, to avoid buying something that will have to be maintained within the historic preservation guidelines, (unless you want something historic to maintain). 

AN LLC has to be set up and maintained properly to have any benefit and by and large, statistically, most people are ill-informed on LLCs and do not run them in a way that actually gives them the protection they bought them for.

I agree on 1031 is the only true way this is a case if you DO NOT want to maintain an investment in real estate. 

It seems the odds are against you recouping your costs if you maintain it over a long enough period. 

Your personal accounts need to be kept absolutely separate from your business accounts if you establish and want to maintain a separate legal entity for your business.

Rentals are probably better, all things considered, but everyone has a different threshold for what they consider hassle and I think a lot of people who are getting into rentals think the hassle is going to be quite a bit less than it actually is.Appreciation is great too, but the way I look at it, that's when you get into the real skill work - finding stuff that will appreciate while maintaining an acceptable level of risk aversion.

The only effect that loosening these rules is going to have are less maintained houses being sold.

All in all I don't think it will be a real issue for any of those things you mentioned, these are built so the two units can operate independently without having to agree on "paying your half of XXX" so if he doesn't maintain his property it shouldn't affect yours.

For the bedrooms we use carpet that is easy to maintain and to clean.

However, we have decided as a society that it is worthwhile to maintain fire departments because the downside of something going wrong, (as rare as it is), is bad enough that it's worth the additional expense.