Personally I'm not at all interested in single moms or raising children not related to me. However I do have some considerations on the subject that I've thought about whenever I've seen the subject be brought up. Nothing really factual or researched, but simply some conjecture on why I don't think redpill claims hold much truth. I will also use Alpha/Beta simply because it makes it easier to explain, don't think too much about it.

So basically, take the basic premise of a woman getting pregnant by an Alpha, then going to a Beta with resources to raise the child with.

If this is true, then first off, the Beta would still be having children with the woman of his own, because if he wasn't having children then his Beta traits would disappear from the gene pool and he wouldn't exist to take care of this woman.

Secondly, the woman would potentially be genetically superior to the Beta if the basic thought is that the womans value is reduced, therefore she has to downgrade to a Beta to get resources. If the woman is genetically superior then the Beta is getting a greater value mate by sacrificing some of his resources for a child that isn't his.

Combine the two and you have a Beta who is basically upgrading his genetic viability by sacrificing some of his resources. Considering this, single mothers wouldn't at all be unattractive, instead they might actually be a MORE attractive option for a less desirable man since he would be increasing the genetic fitness of his children beyond what he could get from a childless woman.

Additionally, investing resources into another mans child in this scenario isn't actually no return necessarily. The reason? This will be an even more genetically fit child with an Alpha father, combined with the resources from the Beta. And while the Alpha Child isn't related to the Beta, he/she absolutely is related to the Beta Children, and therefore it is in their best interest to support them aswell. The results? Betas Children will have the support of an older sibling who is an Alpha Child that was raised properly by two parents with adequate resources. This makes it more likely for Betas Children to survive and reproduce, and have more resources themselves.

TL;DR: By partnering with a woman who has a child from another man, a lower value man can get a higher value woman at the cost of some additional resources, and a child who will increase the fitness of his own children even further. Meaning that it actually makes perfect sense for some men to partner with a single mother from an evolutionary perspective.

I hope my thoughts have made some sense.