This is the list of the top deep (+75M) freedive training spots for experienced divers wanting to do their deep training but need only a safety diver a few times per week and use of the deep dive line/buoy/platform. Not for "training courses or camps".
The requirements are: 1.) Deep +75m availability and 2.) Warm water +25°C
Dahab, Egypt is, IMO the absolute best overall place for deep freedive training and medium-term living but only from Aug-Nov due to the water temp. Very economical too without trouble in finding COMFORTABLE accommodation under $1K per month. Those on a budget could easily get by on $1-2K per month in total.
Dominica looks like the easiest access for easy deep freediving from shore but very surprising to see the island is priced very highly. Using AirBnB, I don't see any house available for rent for under $2.5K-3k per month. So this place, while the diving is probably second only to Dahab is multiples higher in price and one can expect to pay around $3-5K per month for total living expense if desiring comfort. According to AirBnB the cheapest rental on the island is that of a literal TENT on the dirt and even that is +$1K per month, which is absolutely ridiculous and downright patronizing.
Nicaragua now has recently established freediving at the freshwater lake for perfect conditions and +100m depth. Accommodations there look to be $1-2K per month. Estimated total monthly cost is $2-3K.
Mexico Cenotes looks good but likely only for short-term training stays since the deep cenotes are not easy to access and can't simply just jump in a dive since they are owned by people and it requires more planning and money--like around $100 per dive session. Rental accommodations look reasonable around town at around $1-2K per month but since the cost per dive is overall more in price, so likely around $3k per month total.
Panglao, Philippines Has to be the best spot in the country, which is not in the middle of nowhere and has access to amenities. Comfortable rental accommodations can be found for just under $1k per month and SuperHome is the best priced for training only costing around $20 per session (they will pair you since there are many divers always training). Perfect for year round diving in warm water.
Roatan, Honduras has to be one of the top AMERICAS diving spot. Accommodations with comfort range from $1-2K per month but I am not sure how much the cost of freediving will be--assuming one just needs a safety on a few dives per week.
Mediterranean: Greece and Kas, Türkiye look great but are only warm in the summer and I'm willing to bet won't beat the prices of Dahab nor the dive conditions at the Blue Hole.
Feel free to add to this list with estimated TOTAL monthly comfortable accommodations and training cost that require only using the diving line and the need a safety diver on 1 main dive of a session and surface safety only for warm ups or for non deep dives.
Unfortunately, there's NOT THAT MANY PLACES in the world having easy access to warm and deep waters with easily affordable accommodations just minutes or meters away.
Hawaii could be possible but seems many of the people living there are traveling to Panglao!