New Member Still Learning and needing some wise advice

Hi There,
 I am new to this site and new to investing as well, I have alot to learn so all advice is more than welcome.
My question is about some properties we have and what is the best direction to head in.
We currently pay rent ( not a huge deal but I think it is a waste of money) we have moved to a regoinal area. We have 2 properties in  Croydon, Melbourne Vic , which I subdivided afew years ago and  they are both  currently rented. If we are to sell them we could possibly walk away with $300,00.00(Approx) after taxes .
 I would like to sell these properties and buy and build in our regoinal area and make it our primary residence and be mortgage free ( as we do not plan to move, but my husband wants to keep them for the kids ).  My point to him is that there is nothing else we can do to these properties and we have made a great profit, I don't want that to fade  to taxes and inflatation  ( according to the revsed edition this is what can happen).

We also have a house in Portland Which Has just been built and has a tenant in it for 1 year but I am about to sell as this is a high mortgage and requires us to put to much back into it. 

So from all 3 properties I would like to sell become mortgage free ( or just about) and then look to reinvest in positive cashflow or commercial buildings.

So I guess I am asking is it better to be mortagage free ( build and make money on the primary place) and then reinvest or stay renting and keep trying to invest?  I have quickly done some sums and for the two places in Melbourne and the rent we pay we are paying around $20,000.00 a year out of our pocket ( this is a waste to me when we  could be  mortgage free).

Oh on this topic , I read alot of things and talk to people and when the say they have so many investment properties do they own their own house it never states ( this would help me with my question if they did say).

As I am on a roll I also wanted to ask the property in Portland took over 1 and a half years to build ( due to the builder), as I am wanting to sell the property do I have to wait till the tenant has been in there a year or is it from the date I signed the land contract? ( this is to recieve the 50% tax free)

I hope I haven't over loaded you as I said am New and trying to learn as much as I can. I look forward to any responses. 

Kind Regards 

Symone