Since you like planning so much...
You should start a QT and put your first fish (or two) in there. It takes 6-9 weeks to properly QT a fish depending on technique. Petco has a sale on tanks right now ($1 per gallon starting at 10 gallons). So a 20 long for 20 bucks would be a good QT. You could get two 10 gallon ones for tank transfer method. Then after the 2 week tank transfer process is over, you can have it sit and observe in QT for another 4 weeks with maybe 2 prazipro treatments during that time. That is 6 weeks and about as short a QT as I would do.
Tank transfer will take care of ich
Prazipro will take care of internal parasites
The rest of the observation time will take care of almost anything else. Plus it wil give you a chance to make sure your fish is eating well.
Of course, if something else shows up during this time then you need to treat that too. But all this will keep diseases from getting into your DT which can kill all your fish or have you strip down your tank later when it is harder.
Plus, you get to have a fish while your tank cycles