This is my experience, and JMHO, but I think how much household's income is does have some bearing on how a family's intent to or actual fostering is perceived. That is to say that people of higher incomes that foster are more often seen as doing it for "the right reasons" whereas people who may survive on SSDI or perhaps be of lower income may be perceived as doing it for "money only".
Two years ago a person in my DH's social sphere lost custody of his four sons. They (the other members of the family) wanted to keep the boys in the family and one of the sisters ended up getting them. This sister is very low income and it was often said while she was in the process of kinship guardianship that she was just doing it for the money. People told her that to her face; DH's friends are just that brazen. No one took into consideration that those four boys were her nephews and that she probably genuinely wanted them and feared for their well-being if they entered the system.
Now DH and I are in process. Not kinship, just generalized foster/adopt. We aren't wealthy by any stretch of the imagination but we make substantially more than most people in either of our circles. DH is in telecommunications sales and I am a nurse, so automatically people think we are going into foster care because I love kids and NO ONE has commented (to our faces at least) that our motives are anything other than what we say they are. It just seems our decision is more accepted as pure than someone who actually has pre-established ties to particular children. I think socio-economic status does have some role in how foster parents are received...as does personality and lifestyles before the fostering.
In our class of 34 we were the only professional couple there. When they did the brief interview and asked how much we made per year I told her around $95,000. She said wow as if in amazement. I guess she doesn't encounter incomes like that often, but it doesn't mean we're well off. LOL. Far from it. It just means our bills are higher
*Edited because DD was "helping" me type and we got a whole lot of gobbledy gook in there!
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Happily Married for 8 Wonderful Years
Bio Mommy to:

Proud Scholar age 7

Lil' Darlin' (34 week preemie) age 6

Mr. Man age 5

Star Quality age 3
Future mommy to many...I hope...

Our family will grow to 10 by 2010