Sodaqotul jaariya is kind of charity that is its reward is everlasting, as long as element of the charity is still active. This means many years after the death of the doer, he/she will still be rewarded on daily basis.

Quran
The semblance of those who spend their wealth in the Way of Allah SWT, is as the likeness of a grain of corn, which grows seven ears and each ear has a hundred
grains. Allah SWT gives manifold increase to whomever He pleases. Allah All-Sufficient, All-Knowing.” Qur’an (2:261)


Hadith

Abu Hurairah (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "When a man dies, his deeds come to an end except for three things: Sadaqah Jariyah (ceaseless charity); a knowledge which is beneficial, or a virtuous descendant who prays for him (for the deceased)."[Muslim].

According to this Hadith it's three types.

1) Sodaqatul Jaariyah: examples of this include building of mosque, hospital, school, borehole, orphanage-home, donating copies of Quran, etc. As long as people are using this things the doer will be continuously rewarded.

2) Beneficial knowledge he/she pass to People: this include Religious knowledge i.e teaching of Quran, hadith, adkaar, figh, and any other beneficial knowledge. This hadith is the reason why teaching is the best Job in the World!

3) A righteous well-breeded child: This means many years after death of a father/mother he/she could be rewarded through his children/grandchild, provided that he breeded them religiously, and righteously. he has to teach them (children) some important creed (Aqeedah) i.e. making them understand that this earth is temporary exam hall and we have two supervisors (in angels) writing down our deeds and we shall get our uncompromising result on judgement day. It's also noteworthy that this is the most important of the three, because Allah will not punish us if we don't perfrom the first-two, but this. Our creator will punish us if we fail to train our children righteously. This is in Hadith and Quran. i.e. Q66.6

O you who have believed, protect yourselves and your families from a Fire whose fuel is people and stones, over which are [appointed] angels, harsh and severe; they do not disobey Allah in what He commands them but do what they are commanded.

The best gift from a Father to his child is education and upbringing."
Hadith of At-Tirmidhi on the authority of Sa'id Ibn Al-'as.

Even if we don't have money, every child of the Muslim dead can pray for their dead ones.

You don't need paying people to "rain" du'a or recite a thousand Surah for the dead!


...Rabbana-ghfir lana wa li ‘ikhwani nalladhina sabaquna bil imani wa la taj’al fi qulubina ghillal-lilladhina amanu. Rabbana innaka Ra’ufur Rahim.
... “Our Lord, forgive us and our brothers who preceded us in faith and put not in our hearts [any] resentment toward those who have believed. Our Lord, indeed You are Kind and Merciful.”
Qur'an 59:10