You are considering putting a tiny home on your existing property as an ADU or using that money to save up and buy the next investment property and wondering which would be the wiser choice.I think ADUs can help provide additional, much needed, housing.

Yes it exists, but as the above poster mentioned, lots of hoops to jump through.

Also It seems that in my city this doesn't exist with a duplex, triple etc.. 

STRs, including 2 of mine existed before AirBnB.  

Speak with lenders - and consider that although they might agree they could lend to you today - they might not be able to when you need the loan.Unless the existing debt has no due-on-sale provision, there will always be a risk of the underlying loan being called.If it were to be called due:1.

Acquiring pre-existing rental portfolios?

I would recommend leveraging the BP forums to connect with existing syndicators.

If you identify a problem, ask the seller if it was pre-existing or caused by the current tenant.

For existing properties, you must make substantial improvements (equal to the property’s value, excluding land) within 30 months.Ensure the duplex qualifies as an OZ investment and complies with QOF rules.

Quote from @Isadore Nelson: I recently acquired a property with an existing tenant who has been living there for about four years.