I'm somewhat out of touch now so I shall refrain from giving potentially out of date information but there has for sometime now been a shortage of foster carers for local authorities, which I personally would recommend. However current trend of increasing market values and participation of the privet sector in public services it may be that your local authority contract out some of this provision to external agency's
Naturally there will be hoops to jump through and some may seem invasive, but are quite necessary when you think about it. Factors like ones age (unless your very old), occupation, marital status etc. would not be a bar. However they may form part of a complex mix of consideration to appropriate placements, but mainly only when considering cases where there is a particularly complex set of needs surrounding the individual where such factors may be relevant to their care needs.
Conversely factors such as smoking and whether you go down the pub 5 nights a week and come home tiddley (obviously there's nothing wrong with now and again) have increasingly been taken into consideration.
In saying the above I am mainly thinking of long term foster care which is perhaps a bit misleading as most are either short term or respite carers where the need to match up with the young person is not of such great concern.
Sorry if this doesn't rally help but when such things evolve around (in theory in least) the needs of those who care is provided for and the needs of those providing the care, there's no one size fits all approach, and neither should there be IMO.