How to best manage to have two different WP (WordPress) sites on the same host

sorry for been so ignorant.
My case is:

  1. I purchased a domain (say and a host plan for this domain (with no sharing domain capability, i.e. the cheap one).
  2. Later I purchased another domain (say Now they asked for almost $300 in order to upgrade my hosting plan and make it able to co-host the second (or more? I do not care) domail(s).
  3. What is the best way, if any, without upgrading my host plan, to have two different WP installations responding to these web addresses (say and
  4. I know it is possible to have two WP sites hosted under one domain (in my case, say Then, the names would be something like: and domain1/ In that case there is no use for the second domain, is that right?
  5. Is it possible to alias the site physically under subfolders (domain1/ to another domain (say I think not, but need a verification.
  6. What about WP multisites? Is it relevant or can be of some help (concerning the two domain names)?

Many thanks,