I just got a 60's Hawthorne cruiser bike for $25. The only catch to be had was that i need to replace the tires (16x1.75) and had to replace the inner tubes, which was no problem. The main question is that I managed to find some bike tires for about $8 called Kenda K123 street bmx tires which are the same dimensions and are whitewall tires, which normally seem to go for about $20 each, more than I'd like to spend on tires if I can avoid it. The main issue is that I'm wondering if they'll be ok for the bike since they're street bmx tires, not technically cruiser tires, and if they'll interfere with the fenders around the tires (basically if they're larger in any way) Any help would be nice.

I'll attach a picture of the bike and a link to the tires in question.

The Kenda Tires: https://www.amazon.com/Kenda-Street-1...ef=pd_sbs_sg_5

Are you sure you don't need 26" tires? That looks like an adult sized bike to me, but I could be mistaken...

As long as it's 1.75 and not 1 3/4 you'll probably be fine. You can learn quite a bit about the actual circumference of the tire you want here;
https://sheldonbrown.com/tire-sizing.html

Oh, wait. I just clicked on the link and it really does say 16". I'm pretty sure you want 26". Go straight to that Niagara site and look through their on line selection.
Last time I was at Wal Mart they had some whitewall cruiser tires pretty cheap, too.

Virtually all cruisers originally came with 26 x 2.125, 26 x 1 3/8 ("lightweight,") or 24" tires. Fractional 26" and decimal 26" rims are different sizes. Just about any 26" decimal tire will fit on any 26" decimal rim: If there's some space between the tire and fender now, you should have no problem with the classic 26 x 2.125, but going down to a smaller size is no problem, either. Since this rim size is used on mountain bikes, you have a wide selection of tires to choose from.

Actually they are 26" tires, haha. For some reason I always seem to mix the two up, and I'm glad I asked about it before I ordered the tires and ended up with tires 10" too small. I found some sold by the Niagara company for about $16 each (including shipping) which I may just go for if I can't find them cheaply elsewhere, but I will try Walmart. If anyone else knows where I might be able to find some cheaper tires then let me know, but thanks so far for the help and clarification

You may want to compare with Amazon: Sometimes they can be cheaper on shipping, even though you may still be getting the tires from Niagra.

be prepared to wait, my last order from Niagra took forever to get to me.

Looks like a cool old bike but it looks like your fork is bent so you might need to find a replacement for it.

The other thing about ordering Niagara parts through Amazon is that they tend to ship quicker as Amazon has tighter shipping standards.

my last order was through amazon... but maybe I should cut them some slack the parts did come through a hurricane and an earthquake.

I buy from them several times a year, they are always slow, really slow. If you want Niagara pricing, but want Nashbar type service, I haven't found it.