That is probably the easiest way to start if you do not 30-40% cash to put down to make the deals work as an investment from the start. 

I know in theory the process of BRRR, Buy & Flip, Buy & Hold, et... but I am very worried about screwing it up and really putting myself and my family in the hole ( I have a wife and a 1 year old son).

You don't want to put yourself in a situation where you are pinched to make things work personally or for an investment.

I am looking to put a lease together for a mid-term single family rental in South Philadelphia.If you happen to be an experienced landlord in Philadelphia and have a lease you'd be willing to share and I could use at least as my starting point I'd be super grateful.If not, what things should I make sure are in the lease?

We also put in the listing that the renters also have the option of renting the whole unit if they'd like to.

Having a 24 month term on the front end will also make my job easier doing the take-out loan when it's time to refinance into permanent debt, because there's room in there for a full year of tax returns to have been done in the middle (if your exit plan is to sell, it'll also make it easier on your buyer who will presumably be willing to pay a higher price if they can get an A-paper good mortgage).Ask for a 24 month term, tell your contractor you want it done in a year (and make it financially worth their while if they can pull it off), internally/mentally plan on 18 months, and I'm putting you on notice now to do your tax returns on time, rather than extending them (don't fight me on this, please just do it).Trying to get a renovation mortgage like this for only 1 point is likely a waste of your time, but if you want to ask, after you've secured the above as a 'done deal,' go for it, can't hurt. 

Higher salary, stipends etc with the ability to put some roots down and invest a bit so I would highly recommend getting into investing when you are in a better debt situation.

How much do I want to put as a down-payment?

Don't think just because you're putting in nicer countertops and cabinets that renters or buyers will be willing to pay for that.  

In the process of using a quitclaim deed to put it under an LLC and empty the property of personal belongings.