Of course it makes sense to be careful, and to protect yourself financially, but he actually sounds like a good guy.
If what you want is to have him move in to your current home, so you can try living together, avoid having to move somewhere else, avoid having to pay rent, and protect your ownership interests, then I should hope that with a few hours of decent legal effort and a short, well-drafted agreement, that ought to be totally feasible.
As an initial idea, how about something like this:
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Mortgage remains yours and yours alone, as does the ownership of your home;
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You have a legal document between yourselves that makes it very clear that it remains YOUR house and home, and that you have the right to kick him out unilaterally at short notice without having to give a reason.
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He covers 50% of all other household bills, as do you. Presumably this would leave you better off than now, since utilities, telecoms and food costs will not double if he moves in;
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Whatever he was paying before on rent, he instead puts into an account in his own name, but with the idea that he is saving this as contribution towards a deposit on an eventual future home together. So he will be financially better off than before on a standalone basis, but at no incremental cost or risk to you, and the extra money he’s getting will be saved towards a potential future home to be purchased together. And if it does not work out between you, he has absolutely no legal or moral right to stay in your house, plus he has the resources to move out quickly;
If you were to split up, then yes he will have benefitted more than you financially from the time together, but as long as you have also benefitted, maybe that is not so important? Meanwhile your home will clearly remain your home, you will also be better off financially than if you had gone to the trouble of renting another property, you will avoid the hassle of moving, and you could legally and morally kick him out while knowing you had been “more than fair”. While he would benefit financially more than you would from the arrangement, he would bear more of the hassle and risk: he would have to move once in order to move in, and he would take all of the risk of potentially having to move again and find a new place at short notice if it did not work out between you.
Before living together you would probably also benefit from discussing and agreeing upon what would constitute an equitable division of household tasks.
If it all works out, you should have more money and less domestic work in any given month after he moves in, As should he. That is not a basis for a relationship in and of itself, but it could provide a propitious context for the development of a good relationship. Also, if you find that is not happening after a few months, then you will get some very useful information about what he’s like without having had to upend your life.
Just a few ideas ... hopefully helpful, but please ignore if not.