This is the first time I've tried to grow Asparagus from a seedling. In the past I've grown Asparagus from a root ball, which produces fruit much quicker since the root system is already established. It will take 3-4 years for seedlings to reach maturity and start producing a regular yearly harvest, so it is a long term investment. Here is a typical timeline:
Year 1 - Seedling planting (in my region, this is December)
Year 2 - Do not pick any Asparagus
Year 3 - Can pick half the Asparagus
Year 4 - Can pick all the Asparagus
Also, Asparagus create large root balls and should be planted 8-14 in (20-35 cm) apart. I'm growing in containers and planting closer. This is my choice, but not recommended. I will have to feed and water them more and will get smaller Asparagus, but that is my intent. I do not have the space, plus I prefer young Asparagus.
I should also mention that I purchased these from a nursery for 39 Yen (37 cents) each. I bought 10 plants. Quite reasonable! I do grow a lot from my own seed stock, but I also purchase seedlings when I miss planting on time. The generally cost is the same for Tomatoes, Green Peppers and the like.