In terms of investment for building a portfolio, you need to look at equity (in order to duplicate and increase your holdings) so the concern for you is two fold - how quickly can you increase the equity in the loan (how big will the mortgage be? Or will you be able to afford the house outright with the proceeds of sale form your previous house? And secondly, how quickly can you ADD to the value of the house, and therefore increase you equity by increasing the value of the property?
The fact that is a fairly sizeable block is an advantage, as the land and not the house it what is worth money. The land will increase, the buildings decrease in value.
so are you in a financial position to be able to add value to the house immediately?
How quickly are you looking at buying your second property? Which area is the house in? You value increases by a few mehods - 1) natural value increase, around 8% a year on average, 2)Value added by improvements you make and 3) By the houses surrounding it.
For this last reason a general rule of thumb is that you would rather own the worst house in the best street, than the best house in the worst street. Does that make sense? The better your house is when surrounded by lesser houses or area then the less room you have to move. The value of your property will be brought down by dodgy houses. whereas the dodgey houses will increase virtue of being in a 'nice area'.
If you are renting for rental income, as opposed to equity and duplication, you are better off looking at low maintenance properties that attract large rents, generally apartments or units. They are more likely to require less outlay for maintenance and are able to attract higher rents for their added feautres (city apartment blocks are great for this).

Anyway, I hope that makes sense, just some things to think about. If you want to build a portfolio you need to make sure you do your homework - maybe see if you can find out the sale price for similar houses in the similar area over the last 12-24 months, see if you can see how much the average sale price is increasing by.

Hope it all works out for you - it is such a huge decision, all the best.