If you cut the 4" cast iron pipe with a sawzall you can expect to use 3 to 4 good quality blades ans spend 20 to 30 minutes per cut. A much better solution is to contact your local tool rental company and find out if they have a "Cast Iron Snap Cutter"? Most tool rentals have them and charge about $15 a day.
A cast iron snap cutter has a long chain similar to a bicycle chain with raised cutters on the links. The chain is wrapped around the pipe at the point were you want to cut it, then connected back to the snap cutter body. You then turn a crank a few times and you will hear a sharp snapping sound. When you hear the snap the pipe is cut. With a little practice you can make clean cuts in less than a minute, not tht you will be making enough cuts to get a lot of practice...LOL.
When you consider that quality sawzall blades will run $3 to $4 each, the snap cutter will prove to be a bargain in both time and money.
The plumbing codes prohibit installing a Sanitary Tee on a horizontal line so you will be required to install either a Wye & 1/8th bend, a "Combo" or a "Rodding Tee"
If using a Wye & 1/8th bend you should get a "Street 1/8th bend" A "street" fitting has a femal hub on one end and a male raw edge (spigot) on the other end. The male end of the 1/8th bend will fit directly into the hub of the Wye.
A "combo" is one fitting that is premade to the same shape and dimensions as a Wye & 1/8th bend.
You may also use a "Rodding Tee", which is a variation of a sanitary tee only the rodding tee has a radius curve in both directions. Rodding Tee's are made specifically for making a cleanout and may not be used for other applications. This is also the only Tee which may be installed on a horizontal line.
Once you have your Wye &1/8th bend, combo or rodding tee you will then stub up with PVC and place a female thread adapter on top with a clean out plug.
In regards to the drain cleaning machine in your link. A close friend of mine bought one of those machines about 3 yrs ago and I have used it on many occassions. I found it to be a very good machine and comporable to some that i have used in the past that cost many times the price.