I need an inexpensive way to put railing on front porch?

The least expensive is to purchase the pieces and assemble yourself. I would advise pressure treated lumber but know that you shouldn't paint until it has cured (debatable on how long this takes, I would wait 6 months). You can buy small pickets and flat boards for the top & bottom which is the cheapest. Next step up would be buy top & bottom rails that are honed out for pickets and buy the appropriate size for the rails you purchase.

The least expensive that will last at least a little while is to use pressure treated wood. Use the correct size lumber to ensure a safe railing. Check with you town and find out what code is for a railing.

go to the local dump or recycle store & search for an old metal rod iron railing & have it adjusted by a welder to fit & paint it to go with your house. Takes time!!!

PVC pipe painted black.

I got a huge box of spindles and rails at habitat stores for $50. I find it easier to work in wood. I painted it before I put it up.

I actually talked my hubby in to putting barn tin up. He bought 3 wood railings, one top, one middle, and the bottom. He cut tin and used screws to fasten the tin to the three rails. It took one day to put the wood up. It took one more day to cut and screw the tin to all three boards behind the tin. I bought some stars and crosses to put on the tin. I had to order some stars I couldn’t find. Now, just waiting patiently for the rainy weather to subside so we can add my stars and crosses. It is going to look awesome! Thanks for all the helpful suggestions!