Tollie, I read your posts with interest. You do seem to take things on, in a very rational and considered way.
First to assist, it is a pretty well recognised practice in CIM, or CIP, that all that is needed, is one months notice. In QLD at least, all leases tend to be from the 1st of the month. Even if the tenant starts mid month or so, they pay to the end of the month, so the rent is then due on the 1st thereafter.
That having been covered, may I now question you view that it is Ok not to have a formal lease in place. You justify this, if I read correctly, by your flexibility to do renovations etc, which you believe that the lease would have made difficult.
It has been my impression, that the only time a lease, or legal document is taken from the desk drawer, is when there is a disagreement. To have a lease in place, would not have prevented you from doing what you described, as you discused it etc with the tenants. Again, if I read correctly, they would have seen improvements etc, why would they have disagreed ...
Now, my concern is ..... what will you do if things fall off the rails, and in particular ... a member of the public ... is on the property has sustained an injury. You have no documentation to protect your self. If it is common practice, that a LL, has indemnity from tenants, why would your insurer cover you, if they find out, you do not take the "usual" protections etc.
In my ... years, in this business, the greatest fear I have seen amongst people, particularly investors, is personal liability, when there has been an accident, eventuating in a death, and even worst when it is a child. The judgement is in the millions.
That is when clearly defined documents, ie leases, as to who is responsible for what, and backed by directors guarantees when in the case of companies, will be a great bum saviour.
I have no problem with epeople doing as much as they can, firstly to expand their knowledge, and secondly to save money, but on some things, when the risks, ( and they are not obviuos) are high, engage a professional.