On the other hand, I've had lots of homes where either the tanks did not leak or if they did, they used no. 6 oil which is very viscous and does not migrate very far so costs will be limited.  

What is being experienced now is very similar to the 90's in manner of migration paths, developing areas, price ascension etc.

(if that even exists anymore)IMO if you are looking for a rental/ investment property with the goal of property appreciation and decent rent take a long look at Calgary.We are already seeing a lot of migration from Ontario to Alberta and that is only going to pick up as home prices are so cheap.As of this post, there is a full SxS duplex / 3 bedrooms per side for ~$480,000 for BOTH sides

Additionally, migration to Houston from outside of texas keeps these properties moving.

The rental market is strong because there aren't enough quality homes for buyers to purchase and many who migrate here for work are relocated with short notice so they don't have a year to wait on building something new. 

Although the net migration loss is growing there are still some people moving there. 

Then, where will the herd migrate to?

When buying in a city, I’d check migration trends and rental regulations, as well as taxes.

Third, we're seeing a major migration of people with money leaving certain areas of the country and moving to more rural areas, which is depleting the inventory.Keep thinking about what you really want.

There's a lot of people migrating to Texas.