I found this (obvious product pitch) video by Eastwood showing how you can make a good set of A-arms with a few tools. So, I thought you might like to see it.
Now, I'm going to simplify this a bit more. Making it even more in reach for you.
While Eastwood does a good job of how to make an a-arm without a super high end or super expensive shop, they still are trying to convince you to buy things that you don't have to have. Here are some ways you could make this more cost effective for your own use.
If you have a good eye, know how to use a level, pay attention and are willing to do a little bit of prep work, you can bend A-Arms with a pipe bender from Harbor freight for a 1/4 of the cost of the more expensive tube bender you see here. Don't get me wrong; having the nicer, more expensive tube bender will help you attain more consistent and more easily accessible results. Still, with a cheaper hydraulic pipe bender and some ingenuity, you can achieve a very similar result.
Honestly, the best way to notch the tube, is by using a tube notcher as is featured in this video. Considering that the notcher is only $70 normally, and even less when on sale, I say just buy the notcher. In fact, I might actually get me one. However, with a good eye, an angle grinder/reciprocating saw/band saw, and some patience, you can actually create the same effect.
As for welding, you can use a Tig if you have one and know how to use it. However, with the thickness of tube that is typically used on A-Arms (.120" wall) you can also use a stick welder or a mig. You won't be able to get the same finish as a tig, and you may want to gusset a bit more, but there is now reason that these simpler welders can't create a strong enough weld for this application.
Using a powder coating and a media blasting is a great concept, but if you're not making this a production set up, you can use rust converter and a cheap single stage auto paint with a good amount of success as well. Even spray painting can be made to last for a good while if you allow the final product to truly cure before you install the pieces for use. Spray paint (aerosol can) usually requires a full cure time of a week or more depending on the kind of spray paint (aerosol can) it is, and the temp/weather conditions that the paint is drying in. Another cheap and viable option is spray can bed-liner. If the product is prepped correctly, and enough coating applied as directed, the spray can bed-liner should last for very long time.
See, if you're willing to do a bit more work, have a less than flawless product, you too can build just about anything. I mean really, when it's covered in road film, dust, dirt, or mud, does it really matter if you have a tig, mig, or stick weld?
Note: Understand that there are some applications where tig/mig should be used due to thicknesses in metal, contact with straps, hoses, lines, and when welding some times of materials. So, before starting any project research all the factors before starting. Beginners Fab has made the above suggestions based on a thick wall (.120"), mild steel tubing, with a quality weld being preformed and with the appropriate electrodes/wire/gasses being used.