Regarding your question I believe that there are two types of "skin in the game":1) Cash in the deal which ranges from 5 - 20% of the needed equity 2) Signing on as a guarantor on the debtBoth are important, most of the time there is 70% debt and 30% of equity on any specific dealFrom a passive investors standpoint its ideal for the sponsor to be on both ends but its not uncommon for a sponsor to be on neither or one or the other - it simply depends on the specific project and the risk and reward that the project delivers.

Plumbing issues are by no means uncommon, especially in older homes. 40 years isn't too old, but it's not especially surprising to have plumbing issues in them.

This covers the lender in the event there were any mechanics liens or other clouds on title after your purchase.It is not uncommon for the lender to require this. 

It's not uncommon to offer only $100 earnest money or even $10. 

@Robert Burciul It's not uncommon for tenants to receive their security deposit back after living in the property for five years or longer.

Institutions have long used RE as a hedge and alternative asset, very similarly to gold in principle with the idea being an inflation hedge, so it isn't uncommon for investors to have 25% of their portfolio devoted to alternative assets, even if they have no experience in RE at all. 

It is not uncommon for a tenant to break a lease, for whatever reason, and you can too.

Check out my blog post here on BP from a few years ago.https://www.biggerpockets.com/blogs/1028-uncommon-knowledge

On the other hand, I read that California has non-recourse loans, which must be 1/6th of the lending market, so perhaps non-recourse are just uncommon in South Carolina and North Carolina and Virginia and so on.OK well I guess we'll have to chew on this.

I live in a very uncommon market where deals are just different than most places.