On a section of my site, I am currently using .htaccess rewrites to put the ID as part of the URL instead of in the query, like so:

RewriteRule ^([a-z_]+)?/?tours/([0-9]+)/(.*) /tours/tour_text.php?lang=$1&id=$2&urlstr=$3 [L]

For example, if someone goes to /en/tours/12/some-text-here it will rewrite it to /tours/tour_text.php?lang=en&id=12&urlstr=some-text-here. However I don't want the users to be able to put just any text, so if they type in the wrong some-text-here part it will 301 redirect them to the right page.

This works perfectly, but I can see a potential problem potential arising when localizing the website, so I just wanted to make sure it's not actually a problem.

How it is now, if someone goes to /en/tours/12/some-text-here, the anchor to the Spanish version of that page will be /es/tours/12/some-text-here (i.e. only changing the "en" to "es"), and then the script will then 301 them to the correct Spanish text (something like /es/tours/12/algun-texto-aqui). And the reverse will also be the same. The anchor on the Spanish version to the English version would be /en/tours/12/algun-texto-aqui and then they will be forwarded with 301 back to /en/tours/12/some-text-here. Basically, the anchor changes the language and the 301 changes the string at the end.

So I have two questions:

• Does purposely and permanently having invalid URLs on your site that get 301'ed to the correct ones have any effect on SEO? I could make it just show the correct URL to begin with, but this is a significant amount of work due to how I am handling the translations, so I would prefer just to 301 them.
• Will the invalid URLs that are contained in the links be added to the search engine indexes even if they get 301'ed to another page?