Sorry, I don't think this can work. At all.
The last gig I've done on lazy loading and infinite scrolling was the worst project I've taken - under the Your Home biz - and a big factor why I decided to close it. It was, above everything, my mistake on how I was selling my services.
I doubt way too much anyone could want to develop a great infinite scrolling with me. It will be expensive and probably not worth it. There must be lots of folks out there capable of doing more for cheaper. I just didn't have the luck to find their product.
As for the script I've done there and that's not even being used any longer ("We are taking some time to redesign our site. See you next year."), if you really want to go with that, by all means, just take it, use it and abuse it.
If by any chance you're crazy enough to still want to do this with me, do tell. Below there are 2 references of what we could negotiate, with approximate values. Always with open scope, and it needs to be better than what's done in discourse, seo friendly, every single thing done right. I can't settle for any less.
first week for € 1,984. Again, it doesn't mean I'd be able to do it in 1 week, although that could happen.
first month for € 3,876. I'd take 2 weeks to find someone else to code, 1 week to orient them and pay them half, then 1 week to do any adjustments on my own. Of course, in this I'm basically "working" 3 weeks for "free" because that's something I'd really enjoy doing and got little experience with.
None of them have any guarantees. The only thing I can guarantee is I'll be working my ass off 24/7 to make it work, and probably stop everything else I'm doing, during the time I'm enjoying something and, all other times, I'll make at least the 40 hours per week fully dedicated.
I'm not a company, I can't be one right now.