I will share the little knowledge I have on this subject, and I hope it will help you :).
The reason for me to have bought the sawah, was because it (the land) is below my house, and if someone else would buy it and build there...then my view is gone.
I dont know how things work on Java, but here in my neighboorhood the land is being worked on by people who live in the village...what I mean is that I dont think that 'outside the village workers' would be appreciated by the local farmers. So I think if that sawah you are interested in is not within your village-area it would be somewhat inapropriate to have your family work there. Unless maybe if your family not only works your land, but join the other workers and help them too with harvesting and planting.
About the finances...I don't pay any wages or have any expenses (fertilizer and such), whatever comes of the padi 50% is for the villageworkers and 50% for me. Their beras (rice) goes in big sacks to a koperasi where the get money for it. I have chosen to receive my 50% as rice. Saves me having to go to the shop and buy rice, hahaha.
She's right about the three times per year harvesting, but only if you only do rice. you can ofcourse mix it up...two times rice, and one time corn for example...but changing it up means alot of work.
back to finance again...return on investment, depends ofcourse what the initial price per are is, and how much beras per harvest comes of the land. by the way if it's not to forward of me to ask, how much is the price per are in your area? Anyway's in your calculation you can use aprrox. 500 kg of rice (finished product) per harvest per 100 Are of padi.
If you want a bigger return on investment I would suggest growing clove.