Hi there. I did the rent-a-room gig for 6 years - in fact, I'm still doing it - but waiting on the last tenant to move away (by natural means - whenever his circumstances bring that about). During that time, I experienced all - the good, the bad and the ugly.
The difficulty is that you live there - and have daily, ongoing contact with lodgers. That means that if there are issues arising - it makes it all the harder to address them. If you are good-natured, you will be tested. You have no option but to be tough. One thing I learned - is to lay everything down before they move in. Tell them exactly what the story is i.e. that you won't tolerate late payment of rent - not even for a day. Take sufficient deposit to make sure your well covered. If they can't produce a deposit and the first months rent, that should ring alarm bells for you.
I don't know the individuals your dealing with. However, I think at this stage, they feel they are ahead of you - and you don't stand any chance of getting that $ back. If it was me - I would be changing the locks - right now. Bag up their stuff. I *think* by the letter of the law, you can't withhold their property in order to induce them to pay up (others here will be able to clarify this). However, I would be very tempted to withhold (I'm NOT advocating you do this - I'm just expressing how I would feel about a situation like this).
Due to the transitory nature of lodgers, I went through quite a few over the past 6 years. They were very much a mixed bag. The rent a room gig gets bad press from both lodgers and home owners alike. From the tenants perspective, many don't like the dynamic that's in play i.e. that they are in effect subordinate to the home owner in terms of the basis of how things run within the house - despite the fact that it IS also their home. From the home owners perspective, you get issues like you have described. The other issue being that the reality is that nobody cares for stuff that is not their own (to varying degrees - but generally , this is true). I'm talking about fixtures, fittings, equipment, possessions, etc. This can become a point of tension for both parties. I started off probably being a bit too combatitive in this regard. However, what I learnt was - with stuff like that i.e. caring for the place, cleaning up, etc - it's just makes for an easier life just to suck it up - and take care of it yourself (even if that means cleaning up after people - which invariably, it does).
I only really got 'ripped off' the once. It was the one time I didn't take a deposit - and so, that guy left having caused €300 worth of damage. I can only hold myself responsible for that - and it was a lesson learnt. Overall though, it has been a rewarding venture. It has contributed somewhere between €30-€35k to my mortgage. In addition, whilst I didn't get on famously with all - it was definitely an education. I am still in contact with a few of them - and in fact, the very fact that one of them stayed here led to another business venture which has netted me not an inconsiderable sum - and continues to do so.
I know your getting frustrated - given your experience to date. However, maybe it's still worthwhile trying once more. Be a bit more selective - and learn from what went before. i.e. lay it down - NO late payment of rent. The important point here is that becoming a fully fledged landlord is going to bring a new set of problems. Furthermore, you have much less power in this situation - as the law is heavily stacked in favour of the tenant. There are AAM'ers with experience in this area - that can advise you in this regard. In addition, you will have to pay tax on rental income, the property is more likely to take more of a battering and there may be implications for your mortgage (are you on a tracker? Does your loan agreement stipulate that it is for a 'home' loan as opposed to an investment property?). There may also be implications in terms of stamp duty and invariably, your insurance premium on the house will be considerably higher. If you involve a letting agent, then you will incur the cost of this. You are also required by law to register with the PRTB - another cost. Furthermore, you have to pay both household charge and possibly second home tax? Meanwhile - the rent a room scheme - despite it's pitfalls provides you with the ability to take in €10K tax free - and the ability to easily evict a lodger should they behave in the manner you have indicated in your post.
It's definitely worthwhile thinking this through before you make a decision...