If Melinda had gotten $350,000, I believe her elder sisters should at least have a little more than that since the house was given to her too. Perhaps, they got their own share of the properties. But, they seemed broke and had to do difficult jobs to help Melinda get back her house. What had they done with their money? My best guess, they weren't included in the will and it seemed impossible.
Brenda said to Melinda, don't let that guy know mum left you that amount of money in this house.
Apart from that, they were not rich they were just average. Also what you call odd job is not odd to them and don't forget they had reason why they were doing it.
According to the movie, Melinda was the only that got money from her mum's death. It doesn't seem right. The woman gave birth to three daughters and gave all her money to one daughter?
I concluded on that because they never told us if the Brenda and Sarah received anything. If they did they didn't like they had it.
And this on my part isn't possible. All the daughters are at least entitled to the money.