Srm277...a good investment before starting is a soil test. Find out where you are and what is needed to bring the soil to optimum levels. Here in CT, I have mine done every year at UConn (no need for yearly testing but it is interesting to see how it changes).
Results the first year surprised me. The lawn looked good but there was less than 1lb of phosphorus and almost as poor amounts of potassium per acre. Took 60lbs of 10-10-10 and 80lbs of limestone to bring a 40'x 30' garden carved out of the lawn up proper pH and NPK levels.
Your state's soil testing lab is here: Rutgers New Jersey Agricultural Experiment Station
Extension services offer various tests. The cheapest test-- Nutrients, pH and recommendations--has been good enough for me.
NPK levels and pH take a while to rise after fertilizing and liming an area so its best to get started as soon as the ground can be dug for soil samples (I spread black plastic out one year to thaw the ground).
Be a gift to your sister too. She'll know what, if anything, she needs for the lawn, for flowers and whatever else she has growing.