Buy and hold strategy break down

Im new here so not sure if I previously posted this in the wrong sub forum...

Try again.

Hi guys

I am needing some help to set up my investing strategy.

I have explained our situation in a previous thread,
We have approximately $350k in equity to get started with but would like to leave the current investment properties at an 80% LVR leaving us with $150 to spend on deposits.

We are still living in remote FNQ so it may be difficult but my plan is to start out purchasing properties in reasonable areas with reasonable growth and yield such as Logan, Slacks Creek, Woodridge in QLD, Elizabeth south or Salisbury North in SA, Moree & Albury in NSW etc etc. I want to target homes that need work as I am a builder and then renovate, hopefully buying below median house prices and then gaining equity and higher yield. Eventually doing more developments.

So I have a plan in place but everyone always says to start out you need to know where you want to be in 5-10 years time and then work out exactly what properties you need to acquire to get there (how much growth and rental income needed from each property). I think if I follow my plan above I will reach my goals but working out the numbers to get there is difficult as I cant plan how much a knocked around old home in Logan is going to sell for and then how much I need to spend on a reno without seeing the condition.

Iv done some BASIC figures below of an example without doing any renovation work or being active at all, but it looks like a very slow growth to get to where I want to be in 5 years time! Can any experienced investors have a look and tell me their thoughts and tricks:

$160k for deposits

Purchase four homes for $250k each and valued at that price.
Each home rents for $260p/w (lousy yield but worst case scenario)

Use LMI to borrow 88% (unsure of LMI cost so leaving it out)

Loan = $880k interest only, Deposits = 120k + costs = $160k

Rental income o/a = $54080 p/a
Interest o/a @ 4.7% = $41360 p/a
Insurance, managing fees, upkeep allowance o/a = $6326.4 p/a

Net Income from rent = $6393.6 p/a
5% (just an average growth) growth on portfolio = $50k

Now I have outlaid approx $40k in costs purchasing these properties (exc LMI) and I have gained $56393.6 before tax. I understand the following years profits will be excluding the purchase costs which is a bit better and the 5% growth in the following year will be calculated on $1050000.
So the following year I use the $50000 in equity I have gained to buy One more property. This year then looks like this:

Purchase 5th property for $250k at valued price.

Loan 88% interest only = $1100000
Deposit = $30k + costs = $40

Rental income o/a = $67600 p/a
Interest o/a @ 4.7% = $51700 p/a
Insurance, managing fees, upkeep allowance o/a = $7908 p/a

Net Income from rent = $7992 p/a
5% growth on portfolio = $65k

Second year o/a profit before tax = $72992. minus the purchase costs of Prop5.

If I then take the equity and keep purchasing by the 4th year I should be able to purchase two properties.

I understand this is a low Yield and 5% growth isnt amazing but I am no accountant so could someone please jump in and let me know where I am missing things? I want to be able to work out how much I need to be bringing in each year to get to my goals.
I understand newer homes have depreciation on the building and the furnishings which has been great for our first two investments but when spending $200 - $250k on homes they probably wont be new enough.

We want to be aggressive with our investing.

Thanks in advance!