Changing Out cats to IN cats -Help!

Boubou is 12 years old and Charlie is 6 years old.
Both are in/out cats. Because of Boubou's physical condition (back problems) and emotionally unstable character along with our neighbor's constant threats to kill our cats, I've decided to close their in/out door and have closed our large veranda with sliding screened windows. I want to keep them inside the house and teach them to use the litter box. I'm scared stiff of their reaction.
I've invested a lot of money in this new set up because of the terrible problems we have with our neighbor who hates cats - ours and the 15 ferals who come by once a day to be fed. He says they mess up his garden and his son is allergic. On the other hand, Boubou has a tendency to disappear for hours and I'm getting too old to wander the streets of the village at 3 o'clock in the morning calling out "Boubou! Boubou!"..people already think I'm crasy...(not that I care much

The other problem:
In 2005 I brought in a vet and his team and they covered the whole village for 3 days catching, spaying and neutering and giving shots to 119 fereals in the village.
I was charged a minimal amount, but for us, a minimal amount is still a lot because I need money also to feed those ferals that come around once a day. (Although there are other people in the village feeding their "own" ferals).

Now I'm about to bring in another team to catch 5 of "my" ferals who are new and have not been spayed/neutered. this time it's going to cost quite a bit but I have no choice.
I can't have kittens dying of hunger around me and I just don't have any more money.

I have even set up a special area on one side of the house for the ferals to do their "thing" so "my" ferals won't use the neighbor's garden. We have even spent money to bring in someone to clean the neighbor's garden (although we didn't really see any cat feces at that time) and advised him that he could grow special bushes to keep the ferals away . It's not like he has a well-tended garden or anything like that - just an open space around his house he considers "his garden". That's neither here nor there since that's what he thinks. He has a right to think it's a garden...
My husband and I have to face up to constant threats about the ferals who use his garden. We have told him that he can solve the problem very easily by spraying vinegar on the area used by ferals or placing orange or lemon peels. He has already killed my cat Whoopee last year (I can't prove it) and I have had 4 ferals die in front of my eyes from poisoning.(I can't prove it's him). Now he says he's going to court. Actually that's a good thing because this way the situation might resolve itself one way or another. Anyway, according to the law here, hurting, killing or even moving ferals from the area they are used to is punishable by 3 years imprisonment and/or a heavy fine.My neighbor has an extremely violent nature and really doesn't care what the law says.. My husband is scared that he might hurt me. I work from home because I
was in a work accident and can't move around much as a result of the damage done to my lungs from breathing in toxic gas. My husband leaves early and comes home late.

Back to Boubou and Charlie - how am I going to "keep them on the ranch once they've been to town?"
How am I going to litter train them?

Any ideas anyone?
Thanks for the help!
Helen

I don't know if this will help, but I will share ideas.

Get a large litter pan. Some use a low plastic storage container that is meant to go underneath a bed. I use a plastic concrete mixing pan found at home improvement centers. These are larger than those at pet stores.

Use very fine sandy litter. 'Dr Easley's kitten attract litter' works well if you have access to that brand. It is sandy in appearence and contains herbs that are helpful in getting cats to use it.

Make sure you have enough litter pans in areas that they can get to easily. Not close to their food and water.

They should catch on. Good luck with all your efforts.

If the cats are closed into a fairly small area (your veranda, for example) with food and a litter box, they'll catch on pretty quickly. Get litter that is as fine as possible, not coarse, so it will feel more like dirt to them.

Cats do quite well indoors. Better than outdoors, in fact.

In the beginning you could also add some plain dirt from outside to the top of the litter so they recognize it as a place to do their business. You should also have at least 1 litter pan per cat as a minimum and most folks recommend having a spare, i.e., 1 per cat plus 1.

They will probably meow to go outside for awhile but that should gradually decrease so you'll need patience.

My husband was allowing Bijou outside which I hated but had no control over. Bijou finally got hurt and at that point I was adamant that he would no longer be allowed out. We were lucky in that he only cried to go outside for a couple weeks and only whenever we went to the door he usually went out of. After that if he went to the door we only needed to say no and he would walk away.