Hello OP. I have two children as a single parent from a donor, best thing I did in my life.
My advice :
- save money ahead of time
- Make sure as much as possible that you have friends/family willing to help. If you can pay for childcare to have a few hours to yourself a week I'd do that - being a single parent is great but relentless.
- Do NOT enter an informal agreement with a known donor. They could have parental rights and you'd be stuck negotiating with them over the next 18 years. Obviously if co-parenting is something you're interested in then you should look into that, there are websites dedicated to that. But personally I wouldn't, it's all the inconvenients of having a partner without any of the advantages. And if you choose an informal donor agreement against my advice, then do at least make sure they've been tested for STDs.
Personally I feel that the right way to go about it is to go through a clinic, and I would use sperm from an open-ID donor so that the child may find out the man's details once they grow up. It's not about having a father, it's about knowing one's biological origins. It's important to many if not most donor-conceived children and I feel like it's their right to know.
For my children I have also put together a memory box, one for each, with keepsakes and mementos, baby handprints, photos, baby outfits, gift from friends and family to them, and all the donor information so that if I die suddenly they have access to everything. I keep adding stuff to it but less so as time goes by and they're more likely to remember things without needing the mementos.
I was 30 when I chose to do this so your age is not an issue I think. My kids are 3.5yo and 2yo.
Bear in mind that parenting alone is hard and relentless (though less so than being saddled with a useless twat for a partner). So prepare yourself for the fact that when you have a baby leaving the house becomes a military operation.
Also consider how many children you'd want as this might affect which donor you choose (if you want several kids from the same donor you might need a donor with a fair amount of available samples, and if you need to book them in advance so you're sure to have some left for siblings, you may need to pay a large chunk of money for that).
My kids are from the same donor, not just because he's the only donor I really liked, but also because if and when they want to meet him, I want them to be able to support each other regardless of what kind of person the donor turns out to be.
So yeah, lots of things to consider, but very much worth doing !