Long term SEO service for website, between 5 to 20 URLs, 50 to 75 keywords.

Hello! I am looking for a experienced SEO agency/freelancer to perform the following job in a long term business relationship: I have a site now with 2 important urls which are ranking 1 and 5 in a small country in Latin America. The website will start increasing its important urls to between 8 to 12 during the next 2 or 3 months. In the future, the website will continue increasing a few urls because 1 or 2 urls will be dedicated to one type of product or one business line of the company. In addition, there are other urls that are not so important to rank, but the SEO job purpose is to focus on the keywors related to specific products. Then, each URL will be dedicated to cover between 3 to 5 keywords which are the most common keywords used by the users to look for specific products or services. Since the country is small, and the rest of competitors are not spending lots of money in SEO, beating them will be relatively easy for someone who knows what to do. I was able to position in number 1 one url and in number 2 the other url by only registering the company in local business directories and a few of other local places. This was in 2014 and after doing nothing, 5 years later we are still number 1. For the second URL we lost our rank about one year and a half ago and I need to recover it and also rank 1 for the rest of urls and keywords. So... I know what SEO is and I also know that most of the job is at the beginning and then it is easier to keep the top ranks once after reaching #1, so I am not willing to pay a high recurrent monthly fee for a lot of years if all the job has been already done. Once each url reaches rank 1, it will be there for several years and I will add new urls only for new product lines or business lines. Our industry is not too dynamic and the products are not changing every year, so the job is done once and it will last for several years until a new technology is released, which is something that happens between 5 to 10 years. What I am looking: I am looking for an agency/freelancer who can start working with me in the short term to start getting back our lost ranks and also start positioning the new URLs we are launching in the next two months, and then keep working with us in the long term ranking new urls. Initial fee must be low and must be able to grow reasonabily when we add more URLs. The monthly fee must also be reasonable. Ofcourse I do not want anyone to work for free, but I know that most of the SEO job is at the beginning and then the job is reduced. Currently I have: 2 URLs, ranking 1 and 5. By the end of the month I expect to have: 8 to 10 URLs, between 3 to 5 keywords each. In the next 6 months I expect to have: Between 15 to 20 URLs with 3 to 5 keywords each. The SEO service must be targeted for only one country and language must be spanish. Other requirements: Montly reports including all the job done. reports must include: URLs/backlinks. Accounts created with user and password (I will provide email address from my company to perform the SEO job). Any other information needed to keep track of the performed job. All the job done must be white hat. No temporary backlinks of fake job please, like posting backlinks in spammy sites or non relevant niches, etc. etc.. Please feel free to send any message and ask any question. Best regards,