Looking for Cost saving way for guest posting

Hi there, I recently started a guest blogging service for a client to help building healthy links to boost their keyword rankings.
I have tried working with a 3rd party agency to find me good quality referring domains and write the articles to post on the respective referring domains. I have found them quite expensive and moved on to hiring some to write me the content and someone to find me guest blog site. I was successful at finding a good content writer at my expected price. However I am still looking to find someone to help me find quality guest blog site.

If you have been in my shoes, would love to hear your suggestion on how do I find someone for this. Is there any other cost effective approach you have tried?

Also would love your thoughts on best practices for guest blogging that has worked for you?

Thank you in advance

here are a few sources (disclaimer: I only purchased 1 guest post on adsy.com 2 years ago for $28 and the link is still live and d0follow today, but the other sources in this list I haven't tried):

postaga.com
rocketguestposting.com
bloggerspassion.com/guest-posting-sites-list
adsy.com

Fiverr is full of sellers providing cost effective guest posting. You can also search bhw marketplace for the same.

Better try with marketplace for affordable prices.

tazarbm said:

here are a few sources (disclaimer: I only purchased 1 guest post on adsy.com 2 years ago for $28 and the link is still live and d0follow today, but the other sources in this list I haven't tried):

postaga.com
rocketguestposting.com
bloggerspassion.com/guest-posting-sites-list
adsy.com

Click to expand...

Thank you. I will check them out.